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tag:theconversation.com,2011:/us/topics/diamond-1466/articles Diamond – The Conversation 2018-08-23T20:03:43Z tag:theconversation.com,2011:article/101115 2018-08-23T20:03:43Z 2018-08-23T20:03:43Z More than just a sparkling gem: what you didn't know about diamonds
My favourite gem is an occasional series in which we ask a scientist to share the fascinating geological and social features of a beautiful rock.

They're made of carbon – but there's something almost supernatural about diamonds.

Just the word diamond invokes luxury, desirability and toughness. Yet when we think of the element carbon we are more likely to think of charcoal; soft, black, opaque, earthy, light-weight.

 <img alt="" src="https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232028/original/file-20180815-2897-nhgph1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Charcoal is also made from carbon – but it hasn't been subjected to enormous pressures like diamond. from www.shutterstock.com

It's fascinating to see how the crystalline arrangement of carbon atoms transform when subjected to pressures greater than about 40 kilobars (the equivalent of 40,000 Earth atmospheres). These conditions are experienced at depths in the earth from about 120km down.

And some diamonds come from way, way deeper – more than 650km (about the distance from Canberra to Melbourne) into the Earth. Tiny imperfections in such diamonds give us clues about what's happening in the Earth's hidden geological layers.

   Read more: What is a gem? And why painite from Myanmar can fetch US$60,000 per carat

In contrast with carbon in its low pressure form as charcoal or graphite, carbon atoms in diamond are fixed together in a strong, three dimensional network. This leads to unique physical properties: diamond is a clear, extremely hard, often colourless mineral with a very high density.

Diamonds sparkle and have internal fire because of their very high refractive index. This means light is "caught" inside the crystal and re-reflected off the internal surfaces. Faces and facets made by gem cutters accentuate this property.

Violently erupted to the surface

Although diamonds have been prized as valuable gems for a long time, until the early 1700s virtually all traded diamonds came from river gravels (known as "alluvial deposits") in India.

Then in the early eighteenth century diamonds were discovered in Brazil, and from 1866 onwards were mined in South Africa. It was in this country that diamond's major, violently erupted, volcanic source rock known as "kimberlite" was identified for the first time.

This recognition fundamentally changed the diamond exploration and mining industry, and quickly led to vastly increased production and to the high demand from the modern jewellery industry.

Supply of diamonds to the market has long been tightly controlled by a small number of major producers – examples include De Beers (South Africa-Botswana), Al Rosa (Russia), Rio Tinto (Argyle Mine Australia and Canadian mines) and Lucara Diamond Corporation (Karowe Mine, Botswana).

 <img alt="" src="https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=462&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=462&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=462&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232226/original/file-20180816-2891-zhrwea.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 The Diavik kimberlite pipe in northern Canada. John Foden, Author provided

The value of diamonds

Unlike other mined commodities such as copper, gold, oil or coal, diamond has no spot market. Its value is variable and highly subjective, assessed using the "4C" system: colour, clarity, cut and carat (5 carat = 1 gram).

Per carat, uncut diamond values typically vary from around $US10 to $US3000. Very large (sometimes very historical) gem-quality diamonds however may command price orders of magnitude beyond this.

The intensely blue 45.5 carat Hope Diamond started its traded history in India in the early 1600s, and is valued at more than US$200 million. Other recent high-priced diamond sales include the Pink Star (59.6 carats, $US71 million) and the Oppenheimer Blue (14.6 carats, $US57.5 million).

The largest diamond recently sold is the uncut Botswanan 1,109 carat diamond, the "Lesedi La Rona". This sold for $US53 million.

Clues about diamond origins

Many diamonds contain inclusions of other minerals, which are captured samples from the deep Earth rocks in which the diamond grew. These provide important information for geologists.

For example, inclusions of the minerals olivine, pyroxene and garnet tell us their host diamonds grew at depths between about 120 and 300km, in a layer of the Earth known as the sub-continental lithospheric mantle.

This layer is part of the Earth's continental tectonic plates, and lies below the oldest regions of Earth's continental crust known as "cratons". Cratons are up to four billion years old - examples include the Australian Pilbara, the South African Kaapvaal, the Canadian Slave and the Russian Siberian craton.

Blue diamonds deep, deep down

Although the sub-continental lithospheric mantle is the most common source of diamonds, some come from much deeper layers in the Earth.

These are called sub-lithospheric diamonds, and identified by mineral inclusions consistent with being exposed to much higher pressures found at depths of more than 650km.

A recent study looked at a type of rare blue diamond like the Hope Diamond. The researchers consistently detected very high pressure mineral inclusions indicating their diamond hosts grew at depths of at least 660km. These diamonds are blue because of the presence of trace amounts of the element boron.

 <img alt="" src="https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=568&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=568&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=568&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=713&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=713&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232224/original/file-20180816-2906-c0rjwn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=713&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 The Hope Diamond started its traded history in India in the early 1600s. Smithsonian National Museum of National History

The question of how boron ended up at great depths in the Earth's mantle is a fascinating one. Boron is an element that on Earth is highly concentrated in the upper continental crust (less than 20km deep) and in ocean water. Its concentration in deeper mantle rocks is typically extremely low.

Boron then must have been re-introduced to the deep layers where the diamonds grew.

This would likely have happened through a process called deep subduction, where the boundary of an oceanic tectonic plate (about 100km thick) fails, and the plate then collapses into the deep earth's mantle. This moves boron and other materials from the shallow layers of the Earth down into depths of over 700 km.

Kimberlite eruptions then bring the diamonds up towards the surface.

 <img alt="" src="https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=506&fit=crop&dpr=1 600w, https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=506&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=506&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=636&fit=crop&dpr=1 754w, https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=636&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/233194/original/file-20180823-149463-ad5ani.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=636&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Subduction of oceanic lithosphere with boron (B) captured from the oceans and delivered by the subducting oceanic slab to lower mantle depths in excess of 660km. Here the boron is supplied to the growing ultra-high pressure sub-lithospheric diamonds. John Foden, Author provided

A window into deep Earth

In addition to the boron example above, evidence from other diamond mine sites also supports the idea that Earth elements move from relatively shallow to deeper into the Earth through the process of subduction.

This has been detected by tracking different forms of carbon in diamonds from the South African Cullinan mine, and in my own research on mineral inclusions in South Australian diamonds.

 <img alt="" src="https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232228/original/file-20180816-2906-1esf9t9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 A South Australian diamond with visible inclusions. John Foden, Author provided

Deep parts of the Earth still have a physical connection with layers closer to the surface.

So yes diamonds are valuable due to being beautiful, hardy and relatively rare – but they also provide a fantastic window into the structure and the history of our Earth.

John Foden receives funding from Australian Research Council.
 Some diamonds come from depths of more than 650km. Tiny imperfections in these gems give us clues about what's happening in Earth's hidden geological layers. John Foden, Professor, University of Adelaide Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/97084 2018-08-09T20:07:47Z 2018-08-09T20:07:47Z A disappointing earring, and the world's hottest rock: zirconia

Diamond or zirconia? Apart from the price, it can be hard to tell these two gems apart.  from www.shutterstock.com

My favourite gem is an occasional series in which we ask a scientist to share the fascinating geological and social features of a beautiful rock.

Just last week, my partner handed me an earring that she had found in a park near her home more than seven years ago, and for which she'd had no luck finding the owner.

The earring had a gold setting that gripped a very large, transparent, beautifully cut gemstone. Given that I am a geologist, she asked me to check it out for her to find out more about the stone. After all, we thought, if it was a diamond, then it could fund a holiday to somewhere lovely, given its large size. Hawaii, perhaps?

   Read more: Why we value diamond rings and other Valentine's Day gifts

Upon analysing the earring under an electron microscope, it was immediately apparent that the earring wasn't a real diamond. It turned out to be cubic zirconia.

Funnily enough, zirconia is a topic very close to my heart and my professional expertise. In 2017 I wrote a research paper on the "world's hottest rock", and zirconia was part of that story.

 <img alt="" src="https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=782&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=782&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=782&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=983&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=983&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221701/original/file-20180605-175445-18iw252.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=983&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 A false colour image of a grain of zircon (yellow) that has formed a rim of zirconia (multicolours) at 2,370℃ when the surrounding rock melted during an ancient meteorite impact. This is the hottest known temperature to be achieved by any rock naturally at Earth's surface. Nick Timms, Author provided

Crystal lattice gems

Zirconia is a mineral with a crystal structure made from the elements zirconium (Zr) and oxygen (O), with the chemical formula ZrO₂. It looks quite a lot like diamond, but is only worth a fraction of the value because it is manufactured and not a rare natural gem.

Cubic zirconia belongs to a family of zirconia minerals, each having a different configuration of atoms that give rise to different crystal lattice structures, called polymorphs. Similarly, graphite and diamond are polymorphs of carbon – each made entirely of carbon but with different structures.

Like diamond, cubic zirconia is stable at very high temperatures and pressures.

But unlike its sparkly friend diamond, cubic zirconia isn't stable at Earth's surface. In fact, it has never been found in natural rocks, which is why it hasn't been given a proper mineral name by geologists.

   Read more: What is a gem? And why painite from Myanmar can fetch US$60,000 per carat

When zirconia is manufactured for making jewellery, the manufacturers use additives to stabilise it. Impurities are incorporated into the mineral and act like atomic scaffolding, holding the structure together so that it resists transforming into one of the other zirconia polymorphs.

If it is pure, though, it readily morphs into one of its siblings – first to a form known as tetragonal zirconia, then to baddeleyite – a polymorph of zirconia that is stable at room temperature. Every time the atoms shift to transform into a different polymorph, they leave evidence behind within the crystal.

Earth's hottest rocks

So what has this got to do with the hottest rocks on Earth's crust?

I am interested in finding out how Earth responds when asteroids hit it. I have studied a few of the 192 meteorite impact craters that have been discovered on Earth, including the one that was ultimately responsible for ending the existence of the dinosaurs.

Australia has its fair share of craters – Wolfe Creek is particularly well known, made famous by a chilling horror movie.

   Read more: Target Earth: how asteroids made an impact on Australia

Canada's ancient landscape has also accumulated many scars of bombardment. One particular ancient impact structure – Mistastin Lake in Labrador – contains the solidified remnants of a lava flow near its centre that forms huge cliffs called Discovery Hill.

 <img alt="" src="https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=575&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=575&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=575&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=723&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=723&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229920/original/file-20180731-176708-1al832i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=723&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Mistastin Lake in Canada sits in a meteorite impact crater. Google Maps, Author provided

The energy released by the meteorite impact was enough to melt and even vaporise the rocks at ground zero, which then cooled quickly (quenched) to form the glassy black rocks of the cliffs.

 <img alt="" src="https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=138&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=138&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=138&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=173&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=173&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229922/original/file-20180731-176708-1ieoise.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=173&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 The impact structure at Discovery Hill, Mistastin Lake – where the world's hottest rock was found. CLICK TO VIEW. Mike Zanetti, Western University, Canada., Author provided

The rocks had the texture of syrup when I examined them under the microscope, and I could easily see that only a few fragments of the most physically robust minerals had escaped being completed melted.

Frozen in this quenched rock soup were a few little remnant grains of the mineral zircon (with the chemical formula ZrSiO₄). The zircon must have been present in the target rocks before the catastrophic event, and had taken a "hot bath" when they became immersed in the lava.

However, zircon is a tough cookie and doesn't melt when it is heated. Instead, and at high enough temperatures, it decomposes to form tiny crystals of zirconia and liquid silica. The specs of zircon in this particular rock had begun to decompose, reacting within the hot magma and had become encrusted with a beautiful rind of zirconia (the baddeleyite form).

 <img alt="" src="https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=465&fit=crop&dpr=1 600w, https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=465&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=465&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=585&fit=crop&dpr=1 754w, https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=585&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/229926/original/file-20180731-176711-1qocy3i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=585&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Rock collected from the top of Discovery Hill, on the southweastern edge of Mistastin Lake (shown in the photographs above). Mike Zanetti, Western University, Canada, Author provided

My research team could read the paper trail in the baddeleyite, detecting the former presence of cubic zirconia from which the baddeleyite had transformed. This meant that this rock had once been at a blistering 2,370℃ during the impact event around 38 million years ago. This is the hottest temperature ever recorded for a rock anywhere on Earth's surface.

This finding made us wonder what might Earth have gone through early in its history, when it was being bombarded frequently by similar-sized or even bigger impacts, and its surface was subject to these extreme temperatures on a regular basis.

There's an amazing sense of excitement and awe from making discoveries from studying tiny mineral fragments in rocks that spark such deep thoughts about events and timescales almost beyond comprehension. Luckily, this can offset the mild feeling of disappointment after analysing a found earring.

Another time, Hawaii, another time!

   Read more: Life, death and politics in Hawaii: 125 years of colonial rule

Nick Timms does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 Zirconia is a mineral with a crystal structure made from the elements zirconium and oxygen. It looks pretty like diamond, but is only worth a fraction of the value. Nick Timms, Senior Lecturer, Curtin University Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/97453 2018-08-01T04:34:37Z 2018-08-01T04:34:37Z What is a gem? And why painite from Myanmar can fetch US$60,000 per carat

The first three Natural History Museum painites – including one in its natural state with rubies that had been sitting in their collection for years. It had initially been misidentified as the much less valuable tourmaline. © The Trustees of the Natural History Museum, London, Author provided

My favourite gem is an occasional series where we ask a scientist to share the fascinating geological and social features of a beautiful rock.

Humans have adorned themselves and their belongings with attractive stones since prehistoric times. We've used fossil materials such as jet and amber, colourful rocks such as lapis lazuli, and water-clear single crystals of minerals such as amethyst and golden citrine.

The "precious stones" diamond, ruby, sapphire and emerald are distinguished from the remaining "semiprecious stones" largely on the basis of perceived rarity in classical times.

But what makes a stone a gem? It boils down to a few key qualities – beauty and durability. And rarity makes a gem even more special, as is the case for my favourite: painite.

   Read more: Why we value diamond rings and other Valentine's Day gifts

Tough beauty

Any stone may become a gem if it has beauty (in the eyes of enough beholders) and is durable enough to retain that beauty through everyday wear.

Durability usually implies that the stone is hard enough to resist abrasion from airborne sand and dust. Also, that it does not easily fracture or "cleave" on flat planes of weakness (determined by its atomic arrangement).

Diamond, the hardest known material, certainly satisfies the abrasion criterion. A diamond crystal does have four orientations of cleavage plane on which it can be split easily. But for diamonds, this apparent liability can be turned into an asset.

The cleavage is used as a short cut in the early stages of shaping, cutting and polishing this extraordinarily hard material, which is otherwise a slow and painstaking business.

How to cleave a diamond.

The four Cs

Demand drives the value of gemstones as commercial items, and this in turn is a function of fashion and name recognition.

However, the main valuation criteria for gems such as diamonds are often summarised as "the four Cs": carats, colour, clarity and cut.

One carat (0.2 g) is the traditional unit of weight for a gemstone – but larger stones are disproportionately rare, and worth more per weight than smaller ones.

While pure diamonds are colourless, and the same is true of many other gem minerals, striking and rare colours almost always increase their value.

Small amounts of impurities or defects of the crystal structure are needed to produce the prized pink diamonds for which the Argyle mine of northwestern Australia is famous.

Impurities also turn the common mineral corundum into its red form (ruby) and other coloured varieties familiar as sapphires. Such colours are appreciated best through the depths of a transparent, intact single crystal, with the passage of light unimpeded by fractures, inclusions or rough surfaces. Hence the value of clarity.

The rare gem painite

Although diamonds are still the popular epitome of preciousness, they are far from the rarest minerals to have been used as gems.

As a mineralogist, my favourite amongst these ultra-rare stones comes from the gem gravels of the Mogok region in Myanmar. There, sapphires, rubies, spinels and other gemstones accumulate in river beds after washing down from the surrounding forested hills. These have been mined since ancient times.

In 1957, two deep red stones from a batch donated to the Natural History Museum in London – as shown in the lead image for this story – turned out to be completely new to science. A tiny slice from one crystal was used for research, and the new mineral was named "painite" after the original donor, the gem dealer Arthur Pain.

   Read more: De Beers to sell synthetic diamonds: here's how they're made

A third painite was identified in 1979, but it was not until 2001 that a fourth was found in Myanmar. Efforts to find more intensified, working uphill along creeks and locating progressively less water-worn material.

By 2005, a source outcrop for painite was finally discovered, nearly half a century after the original identification. Several thousand stones have now been recovered, but the small number of cut gems remains the preserve of specialist collectors.

Painite's extreme rarity is due to it containing the chemical elements zirconium and boron, which do not normally associate with each other in nature and don't occur together in any other mineral. Ironically, some painite crystals are partly altered to a crust of small pink crystals of the more common ruby.

The increase in supply means that you can now get small crystals of painite pretty easily online for tens of dollars, and poor-quality cut stones for about A$100. However, the tiny proportion of gem-quality stones still fetch US$60,000 per carat.

Opal, the odd one out

The national gemstone of Australia, precious opal, is an anomaly. It is soft enough to scratch easily, prone to cracking, most attractive when nearly opaque, and does not occur as crystals.

 <img alt="" src="https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227121/original/file-20180711-27036-16tz1k7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 A rare example of boulder opal. from www.shutterstock.com

Opal is made from microscopic spheres of non-crystalline silica in a very regular array. This natural "photonic crystal" diffracts light to produce the play of rainbow colours whose beauty overcomes all other considerations.

 <img alt="" src="https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/227119/original/file-20180711-27018-ss54mj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Opal mining creates health hazards in Coober Pedy, South Australia. from www.shutterstock.com

   Read more: From mine to wine: creative uses for old holes in the ground

Where science comes in

The polishing and carving of semiprecious stones originated in prehistory.

But the cutting of diamonds in particular has become a sophisticated craft well grounded in the science of optics. One rough stone may ultimately produce several finished stones of different sizes, the pattern of cuts being chosen to minimise waste.

Diamond cutters angle the facets on each stone precisely, so as to maximise the internal reflection of light and the dispersion of white light into rainbow sparkles. They also aim to produce an overall shape which appeals best to the market.

Similar considerations have led to standard cuts being developed for other gems, to show them at their best.

Andrew Christy does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 What makes a stone a gem? It boils down to a few key qualities: beauty and durability. But opal, the national gemstone of Australia, is an anomaly - it's soft. Andrew Christy, Senior Curator (Mineralogy) at the Queensland Museum and Lecturer, The University of Queensland Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/97558 2018-06-01T09:08:51Z 2018-06-01T09:08:51Z De Beers to sell synthetic diamonds: here's how they're made

  Shutterstock

The world's biggest diamond company, De Beers, recently announced it would start selling synthetic diamond gemstones for the first time in its 130-year history. Artificial diamonds have been manufactured since the 1950s but De Beers has long resisted moving into the synthetic market. The company now believes that technology is efficient enough to produce large quantities of synthetic diamonds with the quality of the best gemstones. How exactly does this process work?

Diamond is highly valued as a transparent gemstone that sparkles like no other. It is also one of the hardest of all materials and feels cold to the touch. All of these remarkable attributes depend on the perfectly regular arrangement of atoms inside the diamond crystal and all these atoms are exactly the same – they are carbon.

Tiny imperfections in this arrangement, whether an atom that's in the wrong place, missing or of a different element, can lead to huge changes in the diamond's colour. For example, replacing one carbon atom in every 10,000 with a nitrogen atom would turn a transparent gemstone brown.

Getting carbon atoms to arrange in this perfect crystal is not easy and it cannot happen naturally on the Earth's surface since carbon here prefers to form crystals of graphite, the soft black, material we use in pencil leads. In this environment, carbon atoms also tend to attach more easily to other atoms such as oxygen and hydrogen than to each other. This means that even making pure graphite crystals is difficult.

'Diamond structure'.

Natural diamonds are made deep inside the Earth where, very rarely, the right ingredients at the right temperature and pressure are brought together and then transported to the surface over millions of years. The first artificial diamonds were made in the laboratory by replicating these conditions in huge machines, and this is still the way that small diamonds for industrial cutting tools are made today.

It is also possible to make high-quality artificial diamond crystals by growing layers of carbon atoms one at a time using methane. This is done by stripping hydrogen away from methane molecules in super-clean vessels using hot plasmas. All the carbon is then forced to grow into diamond crystals, rather than into one of the many other types of carbon such as graphite, graphene or buckminster fullerene (unless of course you want to grow combinations of these very different materials).

The challenge is to make this process, known as chemical vapour deposition (CVD) cost-effective. De Beers now believes it has reached this point and plans to extend production at its facility in Ascot in the UK and at a new diamond factory in the USA.

Controlling the purity of these crystals also opens up new opportunities for using diamond. For example, it's possible to use each atomic impurity as a tiny torch that produces a single particle of light free from interference from its neighbouring atoms in the crystal. This can be used to store a single bit of information for a special "quantum" computer. Impurities of boron, as well as producing valued deep blue or black diamonds, are used to make diamonds that conduct electricity, providing an alternative material to silicon or metals in extreme conditions such as in space.

Each natural diamond carries clues about its unique history and it is possible to reveal its origin by inspecting it with the latest instruments. Artificial diamonds also carry this information and differences in the way they glow in ultraviolet light are regularly used to distinguish natural from synthetic gemstones. So even if the diamond's perfection can't be questioned by the human eye, their tiny imperfections are always there to reveal their hidden histories and their individuality.

Andrew Evans receives funding from EPSRC, the EU(WEFO) and Element Six.
 The world's biggest diamond company is to sell synthetic gemstones for the first time. Andrew Evans, Professor of Materials Physics, Aberystwyth University Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/67685 2016-10-26T18:02:15Z 2016-10-26T18:02:15Z Turning diamonds' defects into long-term 3-D data storage

Diamonds are a data storers' best friend? Diamond image via www.shutterstock.com

With the amount of data storage required for our daily lives growing and growing, and currently available technology being almost saturated, we're in desparate need of a new method of data storage. The standard magnetic hard disk drive (HDD) – like what's probably in your laptop computer – has reached its limit, holding a maximum of a few terabytes. Standard optical disk technologies, like compact disc (CD), digital video disc (DVD) and Blu-ray disc, are restricted by their two-dimensional nature – they just store data in one plane – and also by a physical law called the diffraction limit, based on the wavelength of light, that constrains our ability to focus light to a very small volume.

And then there's the lifetime of the memory itself to consider. HDDs, as we've all experienced in our personal lives, may last only a few years before things start to behave strangely or just fail outright. DVDs and similar media are advertised as having a storage lifetime of hundreds of years. In practice this may be cut down to a few decades, assuming the disk is not rewritable. Rewritable disks degrade on each rewrite.

Without better solutions, we face financial and technological catastrophes as our current storage media reach their limits. How can we store large amounts of data in a way that's secure for a long time and can be reused or recycled?

In our lab, we're experimenting with a perhaps unexpected memory material you may even be wearing on your ring finger right now: diamond. On the atomic level, these crystals are extremely orderly – but sometimes defects arise. We're exploiting these defects as a possible way to store information in three dimensions.

Focusing on tiny defects

One approach to improving data storage has been to continue in the direction of optical memory, but extend it to multiple dimensions. Instead of writing the data to a surface, write it to a volume; make your bits three-dimensional. The data are still limited by the physical inability to focus light to a very small space, but you now have access to an additional dimension in which to store the data. Some methods also polarize the light, giving you even more dimensions for data storage. However, most of these methods are not rewritable.

Here's where the diamonds come in.

 <img alt="" src="https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=588&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=588&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=588&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=739&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=739&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143325/original/image-20161026-11256-1xuba6g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=739&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 The orderly structure of a diamond, but with a vacancy and a nitrogen replacing two of the carbon atoms. Zas2000

A diamond is supposed to be a pure well-ordered array of carbon atoms. Under an electron microscope it usually looks like a neatly arranged three-dimensional lattice. But occasionally there is a break in the order and a carbon atom is missing. This is what is known as a vacancy. Even further tainting the diamond, sometimes a nitrogen atom will take the place of a carbon atom. When a vacancy and a nitrogen atom are next to each other, the composite defect is called a nitrogen vacancy, or NV, center. These types of defects are always present to some degree, even in natural diamonds. In large concentrations, NV centers can impart a characteristic red color to the diamond that contains them.

This defect is having a huge impact in physics and chemistry right now. Researchers have used it to detect the unique nuclear magnetic resonance signatures of single proteins and are probing it in a variety of cutting-edge quantum mechanical experiments.

Nitrogen vacancy centers have a tendency to trap electrons, but the electron can also be forced out of the defect by a laser pulse. For many researchers, the defects are interesting only when they're holding on to electrons. So for them, the fact that the defects can release the electrons, too, is a problem.

But in our lab, we instead look at these nitrogen vacancy centers as a potential benefit. We think of each one as a nanoscopic "bit." If the defect has an extra electron, the bit is a one. If it doesn't have an extra electron, the bit is a zero. This electron yes/no, on/off, one/zero property opens the door for turning the NV center's charge state into the basis for using diamonds as a long-term storage medium.

 <img alt="" src="https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143342/original/image-20161026-11278-1qkd21l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=747&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Starting from a blank ensemble of NV centers in a diamond (1), information can be written (2), erased (3), and rewritten (4). Siddharth Dhomkar and Carlos A. Meriles, CC BY-ND

Turning the defect into a benefit

Previous experiments with this defect have demonstrated some properties that make diamond a good candidate for a memory platform.

First, researchers can selectively change the charge state of an individual defect so it either holds an electron or not. We've used a green laser pulse to assist in trapping an electron and a high-power red laser pulse to eject an electron from the defect. A low-power red laser pulse can help check if an electron is trapped or not. If left completely in the dark, the defects maintain their charged/discharged status virtually forever.

 <img alt="" src="https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143340/original/image-20161026-11239-6taoxb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 The NV centers can encode data on various levels. Siddharth Dhomkar and Carlos A. Meriles, CC BY-ND

Our method is still diffraction limited, but is 3-D in the sense that we can charge and discharge the defects at any point inside of the diamond. We also present a sort of fourth dimension. Since the defects are so small and our laser is diffraction limited, we are technically charging and discharging many defects in a single pulse. By varying the duration of the laser pulse in a single region we can control the number of charged NV centers and consequently encode multiple bits of information.

Though one could use natural diamonds for these applications, we use artificially lab-grown diamonds. That way we can efficiently control the concentration of nitrogen vacancy centers in the diamond.

All these improvements add up to about 100 times enhancement in terms of bit density relative to the current DVD technology. That means we can encode all the information from a DVD into a diamond that takes up about one percent of the space.

Past just charge, to spin as well

If we could get beyond the diffraction limit of light, we could improve storage capacities even further. We have one novel proposal on this front.

 <img alt="" src="https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/143327/original/image-20161026-32322-lvaitv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 A human cell, imaged on the right with super-resolution microscope. Dr. Muthugapatti Kandasamy, CC BY-NC-ND

Nitrogen vacancy centers have also been used in the execution of what is called super-resolution microscopy to image things that are much smaller than the wavelength of light. However, since the super-resolution technique works on the same principles of charging and discharging the defect, it will cause unintentional alteration in the pattern that one wants to encode. Therefore, we won't be able to use it as it is for memory storage application and we'd need to back up the already written data somehow during a read or write step.

Here we propose the idea of what we call charge-to-spin conversion; we temporarily encode the charge state of the defect in the spin state of the defect's host nitrogen nucleus. Spin is a fundamental property of any elementary particle; it's similar to its charge, and can be imagined as having a very tiny magnet permanently attached it.

While the charges are being adjusted to read/write the information as desired, the previously written information is well protected in the nitrogen spin state. Once the charges have encoded, the information can be back converted from the nitrogen spin to the charge state through another mechanism which we call spin-to-charge conversion.

With these advanced protocols, the storage capacity of a diamond would surpass what existing technologies can achieve. This is just a beginning, but these initial results provide us a potential way of storing huge amount of data in a brand new way. We're looking forward to transform this beautiful quirk of physics into a vastly useful technology.

Support for this work was provided by National Science Foundation.

The research is funded by the National Science Foundation
 With current modes up against their limits, we need new data storage solutions. Tiny defects in diamonds' atomic structure might turn them into a new medium for memory. Siddharth Dhomkar, Postdoctoral Associate in Physics, City College of New York Jacob Henshaw, Teaching Assistant in Physics, City College of New York Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/55818 2016-03-09T04:41:32Z 2016-03-09T04:41:32Z Why Zimbabwe's diamond mines need better regulation, not state ownership

Zimbabwe needs more responsible diamond mining companies, not fly-by-night operators Reuters/Goran Tomasevic

Zimbabwe, like many African countries, faces an ongoing struggle to secure fair compensation for its mineral wealth. The question of how to maximise government revenues from the mining sector is a complex matter.

But turning the sector over to state-owned mining companies has rarely optimised mining revenues. What's needed instead are improvements in management practices, regulations, regulatory capacity and the investment environment.

This issue is back in the Zimbabwean spotlight after the country's president, Robert Mugabe, announced that the government will take over all diamond operations. His move came soon after the government failed to renew mining licences. Private mining companies were ordered to cease operations, leave their equipment and vacate their premises.

Diamond mining in Zimbabwe has a short but turbulent history. The country's diamond resources are concentrated in Marange, in its eastern region near the border with Mozambique. A number of private mining companies have operated in partnership with the state-owned Zimbabwe Mining Development Corporation (ZMDC) since the late 2000s. This arrangement began after thousands of artisanal miners were violently forced off the newly discovered alluvial deposits.

The government holds a 50% share in diamond operations through ZMDC. Despite this, it has reportedly received insignificant revenues from the sector in recent years.

Royalty payments, which are calculated on production volume, plunged to a mere US$23 million last year. That's down from US$84 million in 2014. Tax payments, which are calculated on profits, have also been negligible.

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 Zimbabwe may have lost as much as US$14 billion of potential diamond revenue according to former finance minister Tendai Biti. Reuters/Philimon Bulawayo

Zimbabwe's former finance minister, Tendai Biti, recently estimated that mining companies may have looted as much as US$14 billion from Zimbabwe over the past seven years.

Other factors explain declining revenues

It is very possible that the decline in royalty payments and tax revenues is due to production volumes being under-reported, tax avoidance and diamond smuggling. Zimbabwe has inadequate regulation and the diamond sector lacks transparency. But there are a number of other factors that have likely contributed to the sector's declining production and government revenues.

First, Marange – Zimbabwe's largest diamond field – is an alluvial deposit. This makes production at low cost possible, using very basic technology and sometimes even just bare hands. The result has been rapid depletion of the deposit.

Some experts believe that much of Marange's alluvial resources have already been exploited. This would leave mainly kimberlites, which are more capital intensive to produce.

Second, about 90% of Marange's diamonds are of relatively low quality. They therefore don't yield high prices on the world market. They also tend to sell at discounted prices on world markets because of trade sanctions that have been extended to early 2017. These are being enforced by the US and the European Union because of human rights violations.

Third, mining companies have resisted government pressure to develop open-pit or underground operations. Given the low quality, alluvial nature of Marange's deposits and the fact that they are likely already very depleted, it is unclear whether upgrading operations to reach deeper resources would be economically viable.

Even if upgrading operations were feasible, this would require considerable capital investment. Mining companies are unlikely to make these investments because Zimbabwe's business environment is unstable and threatening.

Such an oppressive business environment hits mining companies the hardest. They cannot move their operations elsewhere, as they are tied to where the natural resources are located.

Zimbabwe also has an inclination towards expropriation. It is therefore hardly surprising that mining companies are reluctant to invest, preferring the easy pickings of alluvial mining.

State control

The newly created state-owned Zimbabwe Consolidated Diamond Corporation is set to take over the mining companies' assets and assume all production operations. But consolidating operations under state ownership is not, in isolation, going to solve government's efforts to raise its revenues from the sector.

There is a very good reason that only a handful of state-owned mining companies are engaged in production operations worldwide. Where they have been established they have tended to be less efficient, partly because they are often shielded from competition. They have also been more poorly managed than their private-sector counterparts, leading to deficient outcomes.

Successful state participation in the mining sector is rare. Among the few exceptions are Debswana in Botswana and Namdeb in Namibia. Both are joint ventures between the governments and the diamond giant De Beers. But their experiences cannot be easily replicated in Zimbabwe.

For starters, Zimbabwe's alluvial diamond deposits may be far more fleeting than the deep, extensive deposits in Botswana and Namibia. This makes it improbable that Zimbabwe will enjoy the same long-term horizons as those countries.

Further, Zimbabwe lacks a trusted, experienced and private-sector company with the capital and technical expertise needed to develop open-pit or underground mines. Zimbabwe also lacks the resources to go it alone.

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 Robert Mugabe's plan to consolidate diamond mining under state ownership will not, on its own, increase government's revenue from the sector. Reuters/Philimon Bulawayo

The alternative to state ownership

Rather than state ownership, Zimbabwe needs to improve management practices, regulations, regulatory capacity and the investment environment. Necessary reforms include enacting a comprehensive regulatory regime to govern the fiscal and other facets of the entire diamond supply chain. In addition, Zimbabwe should ensure strict transparency and accountability of the diamond sector.

All mining sector laws and regulations should comply with international standards. These include the Extractive Industries Transparency Initiative and Kimberly Process Certification Scheme minimum requirements. All contracts should be published, together with production volume and revenue information. It is also vital that state-owned entities be subject to the same reporting, disclosure and other requirements as private companies.

The capacity to regulate the mining sector must be strengthened. Relevant regulatory institutions must have autonomy and adequate enforcement capabilities. This is particularly pertinent since the Zimbabwean government will be acting as both a commercial entity and as the regulator.

As a commercial entity it will be aiming to maximise profits, potentially at any cost. As the regulator it will be enforcing environmental, social and other regulations, which may lower the profitability of operations.

Given this conflict of interests, the government may fail to adequately regulate the diamond sector. Otherwise regulatory failures may lead to corruption, revenue leakages, and social and environmental violations.

Finally, it is imperative that government improves Zimbabwe's investment environment to attract more responsible mining companies. Until then, only fly-by-night investors with high-risk thresholds will be willing to operate in its mining sector. But with such investors, Zimbabwe's diamond mining will continue to yield little benefit for the country.

Sarah Logan is affiliated with the International Growth Centre.
 Zimbabwe has said it will take over all diamond mining operations in the country. But what is needed to maximise revenues isn't state ownership, but improvements in existing regulatory practices. Sarah Logan, Economist, International Growth Centre Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/52391 2016-01-19T13:24:05Z 2016-01-19T13:24:05Z Have scientists really found something harder than diamond?

shutterstock Shutterstock

Ask most people what the hardest material on Earth is and they will probably answer "diamond". Its name comes from the Greek word ἀδάμας (adámas) meaning "unbreakable" or "invincible" and is from where we get the word "adamant". Diamond's hardness gives it incredible cutting abilities that – along with its beauty – have kept it in high demand for thousands of years.

Modern scientists have spent decades looking for cheaper, harder and more practical alternatives and every few years the news heralds the creation of a new "world's hardest material". But are any of these challengers really up to scratch?

Despite its unique allure, diamond is simply a special form, or "allotrope", of carbon. There are several allotropes in the carbon family including carbon nanotubes, amorphous carbon, diamond and graphite. All are made up of carbon atoms, but the types of atomic bonds between them differ which gives rise to different material structures and properties.

The outermost shell of each carbon atom has four electrons. In diamond, these electrons are shared with four other carbon atoms to form very strong chemical bonds resulting in an extremely rigid tetrahedral crystal. It is this simple, tightly-bonded arrangement that makes diamond one of the hardest substances on Earth.

How hard?

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 Vickers test anvil. R Tanaka, CC BY

Hardness is an important property of materials and often determines what they can be used for, but it is also quite difficult to define. For minerals, scratch hardness is a measure of how resistant it is to being scratched by another mineral.

There are several ways of measuring hardness but typically an instrument is used to make a dent in the material's surface. The ratio between the surface area of the indentation and the force used to make it produces a hardness value. The harder the material, the larger the value. The Vickers hardness test uses a square-based pyramid diamond tip to make the indent.

Mild steel has a Vickers hardness value of around 9 GPa while diamond has a Vickers hardness value of around 70 – 100 GPa. Diamond's resistance against wear is legendary and today 70% of the world's natural diamonds are found in wear-resistant coatings for tools used in cutting, drilling and grinding, or as additives to abrasives.

The problem with diamond is that, while it may be very hard, it is also surprisingly unstable. When diamond is heated above 800℃ in air its chemical properties change, affecting its strength and enabling it to react with iron, which makes it unsuitable for machining steel.

These limits on its use have led to a growing focus on developing new, chemically-stable, superhard materials as a replacement. Better wear-resistant coatings allow industrial tools to last longer between replacing worn parts and reduce the need for potentially environmentally-hazardous coolants. Scientists have so far managed to come up with several potential rivals to diamond.

Boron nitride

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 Microscopic BN crystal. NIMSoffice/Wikimedia Commons

The synthetic material boron nitride, first produced in 1957, is similar to carbon in that it has several allotropes. In its cubic form (c-BN) it shares the same crystalline structure as diamond, but instead of carbon atoms is made up of alternately-bonded atoms of boron and nitrogen. c-BN is chemically and thermally stable, and is commonly used today as a superhard machine tool coating in the automotive and aerospace industries.

But cubic boron nitride is still, at best, just the world's second hardest material with a Vickers hardness of around 50 GPa. Its hexagonal form (w-BN) was initially reported to be even harder but these results were based upon theoretical simulations that predicted an indentation strength 18% higher than diamond. Unfortunately w-BN is extremely rare in nature and difficult to produce in sufficient quantities to properly test this claim by experiment.

Synthetic diamond

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 Synthetic diamond closeup. Instytut Fizyki Uniwersytet Kazimierza Wielkiego, CC BY

Synthetic diamond has also been around since the 1950s and is often reported to be harder than natural diamond because of its different crystal structure. It can be produced by applying high pressure and temperature to graphite to force its structure to rearrange into the tetrahedral diamond, but this is slow and expensive. Another method is to effectively build it up with carbon atoms taken from heated hydrocarbon gases but the types of substrate material you can use are limited.

Producing diamonds synthetically creates stones that are polycrystalline and made up of aggregates of much smaller crystallites or "grains" ranging from a few microns down to several nanometers in size. This contrasts with the large monocrystals of most natural diamonds used for jewellery. The smaller the grain size, the more grain boundaries and the harder the material. Recent research on some synthetic diamond has shown it to have a Vickers hardness of up to 200 GPa.

Q-carbon

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 Q-Carbon closeup. North Carolina State University

More recently, researchers at North Carolina State University created what they described as a new form of carbon, distinct from other allotropes, and reported to be harder than diamond. This new form was made by heating non-crystalline carbon with a high-powered fast laser pulse to 3,700 °C then quickly cooling or "quenching" it – hence the name "Q-carbon" – to form micron-sized diamonds.

The scientists found Q-carbon to be 60% harder than diamond-like carbon (a type of amorphous carbon with similar properties to diamond). This has led them to expect Q-carbon to be harder than diamond itself, although this still remains to be proven experimentally. Q-carbon also has the unusual properties of being magnetic and glowing when exposed to light. But so far its main use has been as an intermediate step in producing tiny synthetic diamond particles at room temperature and pressure. These nanodiamonds are too small for jewellery but ideal as a cheap coating material for cutting and polishing tools.

Paul Coxon does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 A new "world's hardest material" is proclaimed every few years – but taking the top spot from diamond isn't easy. Paul Coxon, Postdoctoral research associate, University of Cambridge Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/49726 2015-12-22T11:08:37Z 2015-12-22T11:08:37Z From blood diamonds to dirty gold: how to buy gold less tainted by mercury

A speck of gold from a mine in Liberia, Africa.  dw-akademie-africa, CC BY-NC

When a customer walks into a jewelry store, weddings or special occasions are usually front of mind. Rarely does that customer think of where the jewelry comes from, let alone its social and environmental costs.

The tragedy of "blood diamonds" – illegally traded diamonds used to fund conflicts in Africa – has managed to permeate consumer consciousness and generate change, yet most consumers have little idea of where their gold jewelry comes from or how it's produced.

Around 20% of the gold in a jewelry store comes from artisanal and small-scale gold mining. And this sector is now the leading source of man-made mercury pollution in the world, emitting 727 metric tons of mercury into the environment in 2013, more than twice the amount in 2005.

Mercury is a potent neurotoxin that harms the brains, muscles and vital organs of adults and especially children. While most people now know about the threat from mercury in their tuna, few know of its connection to the jewelry on the hand lifting their fork.

Restoring luster to the jewelry industry requires understanding what made it tarnish. A journey to the remote mountains, deserts and rainforests housing the world's gold deposits reveals the story of desperate subsistence miners relying on mercury to make ends meet.

Mercury in gold mining

The artisanal and small-scale gold mining sector comprises 15-30 million men, women and children in over 60 developing countries using rudimentary tools to mine small volumes of gold.

In researching ethics and global businesses, I've dug into how artisanal gold is produced and traded using reports from intergovernmental organizations, nongovernmental organizations and academics, as well as my own interviews with activists and industry representatives.

Mining often occurs informally, meaning that miners forego acquiring permits to work whatever land they can find, be that land owned by large-scale multinational mining firms or ecologically sensitive land protected by the government.

Once miners dig up a portion of promising earth from mountainsides or riverbeds, they grind it, mix it with water and then pour pure or elemental mercury on top, which binds to the gold in the earth thanks to the chemical attraction between the two elements. This divides the slurry into balls of a mercury-gold amalgam and a soup of muddy mercury-laced wastewater called "tailings."

The tailings are dumped into local waterways, where the mercury is ingested by microorganisms and accumulates up aquatic food chains to end up in fish like tuna. Meanwhile, the mercury-gold amalgam balls are burned with blowtorches or on kitchen stovetops, a process which vaporizes the mercury into the atmosphere, leaving behind a semipure, sellable piece of gold.

Miners use mercury because it is the cheapest, easiest and fastest way to mine gold, and because they are unaware of its risks or ways of avoiding them.

Miners buy mercury from local black market dealers and many have no way of knowing that the invisible, odorless mercury vapor toxin is the source of their health problems, since it causes symptoms similar to other local ailments, such as malaria and STDs.

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 Children digging earth for gold in Liberia in 2011. dw-akademie-africa, CC BY-NC

Some miners, such as the Aurelsa cooperative in Peru, have managed to save enough money to upgrade to the cyanide leaching technique used by large-scale mining firms, which as the recent Colorado mining disaster shows, carries its own suite of hazards.

But the experience of miners in places like Tanzania, Mongolia and Indonesia is more typical: families toil for generations without breaking above the poverty line or transitioning to safer livelihoods. Children often skip school to help their families mine, only to fall sick and never return. With no education, their only option is to continue the cycle of mining and poverty as adults.

A top-heavy value chain

With an everyday commodity like coffee, it's understandable why producers don't make much. There's little scarcity in the natural world, and consumers purchase it everyday with little fanfare. But luxury goods are very different. Gold wedding rings are (theoretically…) once-in-a-lifetime purchases steeped in sentimental meaning. People do research and save for years in order to buy a ring that matches their preferences.

My own research shows that the price for an 18 karat gold wedding ring of average size and width can vary from about US$200 at Amazon.com to about $800 at Tiffany & Co. A typical price is around $500.

The value of the gold in a ring is set daily by the London Bullion Market Association. When miners sell their gold into the value chain, large-scale firms earn about 98% of this value, while artisanal miners earn at most 70%. This amounts to $74 for a typical $500 wedding ring and an average annual income hovering near or well below the World Bank's measures for extreme and moderate poverty ($1.25 to $2.50 per day). Without the money to send children to school and invest in cleaner technology, the mercury problem will persist.

So where is the rest of the $500 going? While this varies, my interviews with jewelry store owners in the US, UK and Canada suggest that over 75% of the customer's dollars go to the last two links in the value chain – the wholesaler and the retailer.

The first three links – the traders who buy gold from artisanal mines, the mostly Swiss refineries who purify it, and the manufacturers who alloy it into jewelry inputs – collectively take only 7% of the $500. Compared to the roughly 15% that goes to the miner, it's easy to see why some actors are enjoying market power, while others are relying on toxins to survive.

Fair trade for gold

Until very recently, jewelry consumers were blind to where their money went and whether it supported mercury pollution. Today, however, they can choose to see. Two new value chain certification and labeling programs provide consumers with full knowledge of how and where their gold was produced.

In 2011, Fairtrade International expanded its focus from agricultural goods to minerals by partnering with the Alliance for Responsible Mining to bring the first ethical artisanal gold to market. In 2013, the organizations split and now offer competing programs.

Both programs require miners to acquire permits, use a mercury-reducing device called a retort, and ban children from the mining site. In return, both pay miners 95% of the international gold price plus a social premium miners invest in their communities. Gold sourced in this way that is also fully traceable may bear the program's label. And both programs offer a semi-traceable, non-labeled option for businesses wanting to mix certified with noncertified gold.

Where the programs differ is in their approach to driving demand and thus benefits to miners. Fairtrade pays miners a social premium of $2,000 per kilogram, whereas the Alliance pays them $4,000.

Fairtrade's approach of keeping premiums and therefore jewelry prices low may help drive sales, as may their policy of waiving licensing fees for small businesses. The Alliance's model gives more money to miners upfront, and hopes to offset any lower sales by allowing large businesses to donate to the Alliance instead of sourcing gold from certified mines.

Which organization's approach will result in better poverty and pollution outcomes is an open question. Until we get more money to miners and other subsistence producers, pollution problems will continue.

Currently one in seven people in developing countries die of toxic pollution each year, and 19 million are at risk of mercury associated harm worldwide. This is a horrible price for luxury that the world can't afford to pay.

Kristin Sippl does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 Shopping for a gold ring? New guidelines seek to be the rough equivalent of Fair Trade for small-scale gold mining. Kristin Sippl, Susilo Institute for Ethics in the Global Economy, Boston University Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/32332 2014-10-16T05:26:42Z 2014-10-16T05:26:42Z The rise and rise of Belgium's Indian diamond dynasties

Diamond geezers. Indians are taking Antwerp. Racineur, CC BY-ND

From the outside, Number 2 Hoveniersstraat Street in Antwerp is a nondescript office block. Only the clusters of businessmen speaking in Gujarati on their mobile phones or with each other, give any indication of the hive of activity inside. In the lobby, streams of people shuttle back and forth through the electronic barriers while a queue of visitors waits to have their photo taken and their fingerprints scanned in order to receive a temporary ID card. The business is diamonds. It is a scene repeated elsewhere in the city, and it represents the remarkable and growing dominance of the Indian diaspora in a famous local industry.

As you look along the names on the office doors, what is striking are the names. Whereas a generation ago, the vast majority of them were Jewish, today, a significant majority are of Indian, and in particular, Gujarati origin. Names like Mehta and Patel are particularly common. Indeed, while the orthodox Jewish presence in Antwerp is still highly visible, the numbers have dwindled over time, as a new generation of young and dynamic entrepreneurs from the Gujarat have displaced them. It has been unexpected, so what is the secret to their success?

The diamond industry cannot enforce written contracts – diamonds are easily portable, universally valuable and virtually untraceable, and state courts are incapable of enforcing executory contracts for diamond sales. It operates on credit, relies on trust, and hence favours tightly knit community and family-based business networks. The Orthodox Jewish community in Antwerp had long relied on the effective social control mechanisms of their community in order to ensure trust, with anyone seeking to cheat seeing their reputation and hence ability to do business quickly destroyed. Gujarati business communities operate along similar lines, with strong family networks and a high incidence of marriage within their ethnic group. In the Gujarati case however, an additional source of community cohesion, support and solidarity comes from their caste community.

Building from the bottom

My interviews with Gujarati traders show that beginning in the 1960s, the first Gujaratis, from the Jain community and known as Palanpuri Jains, from the area of Palanpur in Gujarat, began to arrive in Antwerp, the world's biggest trading hub for rough diamonds. The Palanpuri Jains are a historic "business community" in India that has traditionally engaged in trade and hence their first foray into Antwerp was one based on capital and prior experience on the polishing side of the diamond trade in India.

The Gujarati Jains took advantage of two key factors to enter into the closed world of Antwerp's diamond industry: they started to specialise in smaller, lower-value stones, and used the cheap labour and excellent skill of Surat's diamond cutters and polishers to produce diamonds that had larger market potential. Thus, Gujaratis were able, as one trader put it: "to polish in rupees and sell in dollars".

These two factors, along with others, such as initially buying from source and offering longer buying periods on credit in order to undercut the competition, enabled the Gujaratis to gain a foothold in Antwerp. Many of the early traders also mention English as the international language of diamonds further facilitating their entry into the field.

This foothold has now expanded to such an extent, that in the latest elections to the Antwerp World Diamond Centre in 2012, five out of the six representatives elected to the board were Gujarati. In 2014, a Gujarati businessman was nominated vice president.

Dynasty

However, when we speak about Gujaratis in the diamond industry in Antwerp, we are in fact referring to just two communities which have come to dominate the trade – the Palanpuri Jains and the Katiawadi Patels. The latter are a community that in just one generation has distinguished itself with a dizzying rate of social mobility. The Katiawadi Patels were once agricultural labourers who moved to Surat (Gurjarat's diamond polishing centre), in order to escape drought. They started off as cutters and polishers, but quickly moved up the ranks and over time accumulated enough capital to open their own factories. They were able to use their contacts with Palanpuri Jains in order to first establish themselves in Antwerp. Once they did, they rapidly expanded and now rival the Jain Gujarati traders there.

Although the Patels did not arrive with the same level of financial capital as the Jains, their control of diamond polishing in Surat means that their climb within the industry is secure, and indeed will continue to grow with time. Currently, most factory owners and managers in Surat are Patel, with workers now coming from other states. In contrast to the Jains, whose sons have more business opportunities available to them, the sons of the Patels, who rely more heavily on diamonds, continue to enter into the diamond business in large numbers, starting from a young age to visit their fathers' offices to learn the trade. The growing prominence of the Katiawadi Patel community has led to tension in India´s diamond trading centre of Mumbai. In a recent hotly contested decision to move operations to Surat, where rent is cheaper, the diamond community was divided between the Palanpuri Jains, who prefer to remain in Mumbai, versus the Patels who pushed strongly to shift to Surat.

 <img alt="" src="https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/61534/original/xkfhg8k4-1413204078.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Modi presses the flesh in DC. Speaker John Boehner, CC BY

The Gujarati-dominated diamond industry has recently been receiving more attention from one of their own, India's new PM Narendra Modi. The 2014 budget passed by the Indian government gave a strong fillip to the diamond industry in the region, by raising custom duties on the import of polished and semi-polished stones, which will protect local polishing jobs (the diamond industry employs 500,000 people in Gujarat). The Modi government has also recently announced that it will be building a fast train linking Mumbai to Ahmedabad, which will cut the current travel time of seven hours to just over two hours. Gujarati traders in Antwerp eagerly await a visit from Modi, in whom they have invested high hopes for boosting the diamond industry. Although based in Antwerp, the diamond business is intricately linked to the Indian economy, immediately affected by Indian policy, and frequently connected to transnational family businesses that span multiple continents. The industry faces a number of challenges, from growing competition from the internet and from China/Hong Kong, to the rise of synthetic diamonds, and the decision by De Beers, the largest company by revenue, to move the sorting and trading of rough stones from London to Botswana.

However, in order to continue to shine, both Gujarati communities would do well to look towards a group that is currently completely overlooked in the diamond business: women. Daughters are not encouraged to enter the diamond trade, with many traders claiming that they are simply "not interested", and the few that do, are not taken seriously and consequently drop out when they get married. The diamond industry in Antwerp is currently even more male dominated that most national armies. By not cultivating the talent and skills of their daughters, Gujaratis are losing out on even more sparkle.

Kathryn Lum does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 From the outside, Number 2 Hoveniersstraat Street in Antwerp is a nondescript office block. Only the clusters of businessmen speaking in Gujarati on their mobile phones or with each other, give any indication… Kathryn Lum, Research Fellow Migration Policy Centre, European University Institute Licensed as Creative Commons – attribution, no derivatives. tag:theconversation.com,2011:article/9719 2012-11-08T03:25:32Z 2012-11-08T03:25:32Z More than a gemstone: using diamond for next-gen electronics

Diamond: more useful in the lab than on a finger. Charlene/Flickr

Diamond is well known for its appeal as a gemstone. Perhaps less well known are some of its extreme material properties.

As well as being the hardest material in nature, diamond is very good at conducting heat (at elevated temperatures) making it an ideal material for heat-management applications.

Diamond also has very high electron and hole mobilities – that is, it's an excellent conductor of electricity, when the material is suitably doped.

Fundamental research

My colleagues and I at the University of Melbourne and La Trobe University are harnessing some of these less-well-known material properties of diamond in order to, hopefully, develop the next generation of transistors. Transistors form the building blocks of computer chips which can be found in devices such as laptops and smartphones.

We're investigating the fundamental behaviour of charge carriers in [synthetic diamond](http://en.wikipedia.org/wiki/Synthetic_diamond#cite_note-isberg-75 – that is, how electrons and holes – a theoretical lack of an electron and therefore a positive charge – behave in diamond.

Future transistors will ideally operate at much higher speeds than conventional transistors and their working might not be based on electrical charge, but rather on the "magnetic moment" (imagine a tiny magnetic field) of individual charge carriers.

This magnetic moment is referred to as "spin" by physicists and can display quantum mechanical behaviour. The emerging field of technology known as "spintronics" is focused on building electronic circuits based on this physical quality.

Superconducting diamond

It has been predicted and recently shown by several groups that a superconducting state (a flow of electric current without any resistance) can exist in diamond films that are doped to a very high concentration with boron atoms.

 <img alt="" src="https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/16695/original/3g9y6vt3-1350562258.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 PhD students Mark Edmonds and Nina Eikenberg (pictured) use a new cryogen-free dilution refrigerator, which can create the coldest macroscopic place in Victoria. Peter Casamento

We are trying to observe the same phenomenon in nitrogen-doped ultra nanocrystalline diamond (UNCD) films, for which the charge carriers are electrons, rather than holes.

This work could result in a new class of diamond-based, high-temperature superconductors with sensing and device applications.

For our experiments we use a recently commissioned dilution refrigerator to subject our samples to a broad range of temperatures.

The operation of this particular fridge does not rely on liquid helium (an expensive and finite resource) but it can cool down to a minimum temperature of roughly 10 milli-Kelvin (-273.14℃) – more than 100 times colder than the average temperature in space.

Solids and phonons

In solid materials, atoms are typically arranged in a periodic fashion, which scientists refer to as a lattice. By stacking layers of these lattice planes together, we can eventually form a crystal. A solid is typically comprised of many crystals (polycrystalline material), but can also be made up of a single crystal only.

It is very difficult to synthetically grow a large piece of high-quality, single crystal diamond, as it must be grown from a single seed under very precise growth conditions. This is one of many reasons gemstones, such as diamond, can be so expensive.

Generally, the atoms in a crystal are not static – they vibrate back and forth. At room temperature, there is enough thermal energy to shake the lattice continuously.

These thermally activated vibrations are called phonons. Phonons play a major role in determining the physical properties of solids, such as the thermal and electrical conductivity, because of their interaction with mobile charge carriers.

At dilution refrigerator temperatures, however, there is not enough thermal energy available to shake the atoms and the presence of phonons is drastically suppressed. This implies that mobile charge carriers in solids can become free of interacting (scattering with) with phonons, and their true quantum mechanical nature can be revealed.

 <img alt="" src="https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=532&fit=crop&dpr=1 600w, https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=532&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=532&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=669&fit=crop&dpr=1 754w, https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=669&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/17220/original/yvcy2pnf-1351853025.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=669&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Micrograph of synthetically grown diamond crystals using the chemical vapour deposition (CVD) technique. Prawer

Two diamond devices

As part of our research, we're currently investigating two different types of diamond devices.

Nitrogen-doped UNCD:

The first device type is made from nitrogen-doped (20%) UNCD and is arranged as a Hall bar – a standard shape used in solid-state physics (see image below) which can be used to determine the density and mobility of charge carriers in the device. We do this by applying a [magnetic field](http://en.wikipedia.org/wiki/Magnetic_field](http://en.wikipedia.org/wiki/Magnetic_field) perpendicular to the sample surface.

The nitrogen-doping provides excess electron charge to the diamond, which is otherwise electrically insulating. These excess electrons are mobile and are therefore responsible for the flow of electricity in this material.

The UNCD films we are investigating are polycrystalline materials consisting of ultra-small diamond grains ranging from 2-5 nanometres up to 1 [micron](http://en.wikipedia.org/wiki/Micrometre](http://en.wikipedia.org/wiki/Micrometre) in size. Due to the small size of these grains there is a lot of surface area that interconnects these grains, as opposed to a single crystal of diamond.

It is these boundaries between the grains where impurities ("dopants") are most likely to migrate to and contribute to electrical transport.

We therefore expect that not only the doping concentration, but also the size of the crystals – and therefore the surface area in between the grains of the poly-crystalline film – play an important role in the conductivity of the material.

Single crystal diamond:

In contrast, the second device type is a Hall bar transistor fabricated out of synthetic (i.e. lab-made) single-crystal diamond, which contains very little nitrogen.

To create excess charge carriers in these high-quality single crystal diamonds we use a technique called [hydrogen (H)-termination](http://en.wikipedia.org/wiki/Hydrogen-terminated_silicon_surface](http://en.wikipedia.org/wiki/Hydrogen-terminated_silicon_surface). Here, we expose our crystals to a microwave plasma containing hydrogen gas, which in combination with a thin water layer, introduces a hole-type surface conductivity.

So, in these hydrogen (H)-terminated crystals the majority charge carriers are holes rather than electrons and the current flows on the diamond surface only, rather than in the bulk of the crystal.

 <img alt="" src="https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=457&fit=crop&dpr=1 600w, https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=457&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=457&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=575&fit=crop&dpr=1 754w, https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=575&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/16279/original/bzvh8x23-1349668356.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=575&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
 Optical micrograph of the single-crystal diamond Hall bar transistor. The green-blue area has been hydrogen terminated, and is conducting. Everywhere else an oxidation process has removed the hydrogen termination rendering it non-conducting. The current flows in the horizontal direction and both Hall voltage (transverse) and longitudinal voltage are recorded as a function of the applied magnetic field. Edmonds

In order to determine the fundamental properties of the charge carriers in our diamond samples, we used a standard method in physics, usually referred to as the Hall effect. Here, the electrical current through the sample (in this case the diamond devices) depends on the intensity of the magnetic field applied to the sample.

This relationship allows us to determine fundamental properties of the charge carriers, such as density and mobility. This is then repeated for different temperatures to see if the material behaves as an insulator or metal.

Experimental results

From the preliminary low-temperature measurements we have performed so far, we have learnt that the UNCD samples behave as insulators. That is, the electrical current disappears when you drop the temperature below a certain point – somewhere between 1 and 10 Kelvin – depending on the doping concentration.

Other research groups have demonstrated otherwise and therefore more work is needed to reconcile our data with their published results.

The single-crystal diamond samples, however, conduct electricity all the way down to the lowest possible temperatures the dilution refrigerator is capable of reaching (10 milli-Kelvin) and display only moderate temperature dependence.

Future prospects

So, what does all this mean?

First of all, it's worth noting that our research is fundamental in nature and is, as such, not application driven. That said, as more and more scientific knowledge of charge carriers' behaviour becomes available, our research might be applied to the design of future transistors and/or sensors.

In the near future we want to create nanometre-scale electronic devices in diamond using the electron-beam lithography facility at the Melbourne Centre for Nanofabrication (MCN). Such ultra-small devices will lead to novel bio-compatible sensors – such as has already been used in the Bionic Eye – and diamond transistors whose operation will depend on the presence of a single hole charge.

Importantly, we have recently succeeded in passivating (protecting by overgrowth) the H-terminated diamond surfaces with an alumina capping layer. This means that the technology for implementing surface conducting diamond into device applications is now more robust and might become a reality.

So, the next time you look at that diamond engagement ring on your finger, stop and think for a moment. There's a lot of fundamental physics living below that shiny surface.

Laurens H. Willems van Beveren does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
 Diamond is well known for its appeal as a gemstone. Perhaps less well known are some of its extreme material properties. As well as being the hardest material in nature, diamond is very good at conducting… Laurens H. Willems van Beveren, Senior Postdoctoral Research Fellow, Solid-state Physics, University of Melbourne Licensed as Creative Commons – attribution, no derivatives.