By Abby “Opal” Ritz and Helen “Azurite” Warfle

On the first day of class, Professor McCoy asked us what our favorite rock was. Now that the semester is almost over and we have a more advanced knowledge of geology, we have decided to come back to this and give everyone a description of their rocks and note whether or not they are significant in the Broken Earth trilogy. It is clear that in the beginning of the semester, none of us knew the difference between a rock and a mineral as most people chose minerals, except for those who chose igneous rocks, sedimentary rocks, granite, slate, and shale (good job lads, you rock 😉 ).  

    • Igneous (x3)
      • Igneous rocks are a general category of rock that are formed when lava cools and solidifies. There are two types: intrusive and extrusive. Like the name suggests, intrusive igneous rocks form inside the earth. They take a very long time to cool, so the mineral grains have time to grow much larger. In contrast, extrusive igneous rocks cool very quickly and have very small grains and thus are fine grained or glassy in texture. Notably, Syenite is a type of intrusive igneous rock formed with alkali feldspar and ferromagnesian mineral. Damaya chose this name because under heat and pressure, it grows stronger, not weaker, just as she did in the Fulcrum ( The Fifth Season 331).
    • Sedimentary (x2)
      • Sedimentary rocks are another category of rock formed of particles, known as sediments, that have come together. These particles can be other rocks or the remains of biological organisms. Common sedimentary rocks include limestone, sandstone, and shale. The one that have more distinctly seen sediments are known as clastic sedimentary rocks and are called that because the larger pieces of pre-existing rock are called clasts. Biologic sedimentary rocks are formed when large amounts of organisms die and become cemented together. Though sedimentary rocks do not feature prominently in the Broken Earth trilogy, their formation can be seen as a metaphor for Essun. Like a sedimentary rock, Essun’s final form is built upon other identities and the accumulation of lives and people, adding layers to who she is as a person. This culminates in her stone-eater form, which would be considered the final form of the sedimentary rock. Sedimentation can also be seen as an obfuscation – dead-civ ruins are often mentioned as being hidden by rock, and though they may not necessarily be sedimentary rocks, this creation of layers of rock and history is very similar to the way that these rocks form.
    • Diamond (x2)
      • Diamonds aren’t actually a rock, they are a type of mineral, but it can be found in both igneous and sedimentary rocks. It is the hardest mineral with a 10 on the Moh’s Hardness Scale. The diamond that Nassun found in The Obelisk Gate is what outed Uche as an orogene to Jija and really what started the whole series. There is a diamond obelisk, and stone eater teeth and bones are made of diamond as well. Diamond is also used to describe Essun; Nassun thinks “Mama often held herself the same way, feeling of soft dignity layered over a core of diamond obstinacy” (The Obelisk Gate). Thus, despite being not as obviously important as other rocks and minerals, such as onyx, syenite and alabaster, diamond plays an important role.  
    • Basalt
      • Basalt is a type of extrusive igneous rock that can also form in shallow parts of the earth’s crust. Made up of plagioclase and pyroxene, It is the most common type of bedrock, as most ocean basins are lined by basalt. The moon is also covered by basalt and its highest mountain, Olympus Mons, mostly made of the same rock. It follows that the Moon in the trilogy would also be made out of basalt, though there is no way to confirm this. Basalt also surrounds the area of Found Moon.
    • Slate
      • Slate is a metamorphic rock that was originally shale or mudstone. Interestingly, the term slate was once used to include both slate and shale, but this is out of practice among geologists. Slate is shale further along the metamorphic process. This rock has a very thin cleavage, which makes it ideal for producing sheets of it for use in building. For this reason, its primary function in the books is as part of buildings.
    • Garnet
      • Garnets are a series of eight minerals, all of which bear the name of the gemstone but have slightly different colors and chemical makeups, but the two most commonly used are almondine and pyrope. These two are known together under the name carbuncle, but this term is rarely used anymore. In The Broken Earth trilogy, there is a garnet obelisk that is part of the Obelisk Gate and is the one that Hoa was trapped in in The Fifth Season, and that Syenite called upon to (accidentally) destroy Allia.
    • Graphite
      • Graphite is another mineral found in metamorphic and igneous rocks. It has the same chemical composition as diamond but very different properties. Ironically, diamond is the hardest mineral, but graphite is one of the softest; it has a ranking of 1-2 on the Mohs hardness scale. In this aspect, it is very similar to alabaster, which has a hardness of 2. It is ironic that alabaster is so soft, because the Alabaster we know is tougher than diamond.
    • Obsidian (x3)
      • Obsidian is a type of (usually extrusive) igneous rock that forms when molten rock cools very quickly, resulting in no crystalline structure being formed. For this reason, it is classified as a mineraloid and is often called volcanic glass. Though most people think of it as black, it can come in other colors, including one called “snowflake obsidian” that has white spots. We were showed a sample of this in Dr. Farthing’s lab. Obsidian features most prominently in The Fifth Season as the walls of the Black Star and the Fulcrum have obsidian walls. Additionally, in The Stone Sky, the stone forest Castrima comes across is made of obsidian, which is what tips off Essun to the danger within, as only an orogene could have made the forest, as natural stone forests are made of limestone. In this series, obsidian represents hidden danger in the form of the Fulcrum and the stone forest trap.
    • Philosopher’s Stone
      • A stone with the supposed ability to transform base metals into gold/precious metals. The Philosopher’s Stone provides not only wealth, but an “elixir of life” through which one can receive eternal life and cure illnesses.  The philosopher’s stone is related to the practice of alchemy, which was concerned with “the perfection of the human soul.” Many of us would likely associate the Philosopher’s Stone with the Harry Potter series and the character of Nicolas Flamel, who achieved close to eternal life through the discovery of the stone.  Flamel was, in fact, a real person, who claimed to have transformed lead into gold after decoding a book af alchemy — the truth of this can’t be corroborated, but he did become pretty wealthy at this time (donated his wealth). Searches for the Philosopher’s stone in the Middle Ages led to various scientific discoveries that would lead to chemistry, pharmacology and metallurgy. Though there is no philosopher’s stone in the trilogy, the making of stone eaters is similar to the process the philosopher’s stone is supposed to be able to do. The transformation of flesh into stone would be considered a form of alchemy in our world, and in this manner, Father Earth and the stone eaters play a similar role to the philosopher’s stone.
    • Emerald
      • Emerald is a form of the mineral beryl, which can be found in igneous, sedimentary, and metamorphic rocks. Though it is very hard, with an eight on the Mohs hardness scale, most samples have flaws or fractures in them that make them prone to breaking. There is no large-scale emerald obelisk that is mentioned, but there is a scale model in the control room from The Stone Sky, so it can be presumed that one exists.
    • Rose Quartz
      • Rose quartz is another mineral; specifically, it is a form of the mineral quartz with small particles of dumortierite, which gives it its distinctive color. There is a quartz obelisk that is part of the Gate.
    • Granite
      • Granite is a light colored igneous rock with grains large enough to be visible.  It is generally composed of quartz and feldspar, with various amounts of other minerals; the mineras give granite a red, pink, gray or white coloring. Granite is famous, everyone, it is the most well-known igneous rock, likely because it is one of the most common rocks found at the earth’s surface and is used to make various objects we encounter in everyday life, most notably tasteful countertops.  Under the commercial definition of granite — wherein granite is defined as a rock with visible grains that are harder than marble — gabbro, basalt, pegmatite, schist, gneiss, syenite, and a few others are categorized as “granite.” Granite is the most abundant rock in the continental crust and is generally hard enough and inert enough to resist most weathering, very strong, and is easy to polish.  The most notable mention of granite in the trilogy is likely that Steel (or Remwha) is composed entirely of granite, which is a deviation from most other stone eaters, who are generally composed of a variation of different rock and mineral types.
    • Sapphire
      • Sapphire (as well as ruby) is a form of the mineral corundum. Corundum comes in many colors, so the blue ones are known as sapphires, the red ones are rubies, and any other color is called a “fancy sapphire.” For this reason, it is interesting that this is the obelisk that Nassun is most connected to, as it is the mineral that her half-brother was called. As Essun notices when she first opens the Obelisk Gate: “Sapphire.  It resists being pulled into the network of the Gate. You barely noticed before, overwhelmed as you were by dozens, hundreds of obelisks, but you notice now because NASSUN IT’S HER It is your daughter, it’s Nassun, you know the stolid complexity of her as you know your own heart and soul, it’s her, written all over this obelisk…” (The Obelisk Gate 376)  This familial link is definitely an easter egg (or a chalcedony geode) that Jemisin has hidden for those who know geology.  
    • Geode (x2)
      • Geodes are formed when precipitated mineral material fills the space inside a hollow rock, generally through concentric inward growth wherein the material builds up over a long period.  Geodes generally have a durable outer layer which is more capable of surviving weathering than the surrounding bedrock, meaning that geodes often eventually separate from and survive their host rock. Geodes are generally formed in either: sedimentary environments or volcanic environments.  Sedimentary geodes are found in limestones, dolomites, and calcareous shale, wherein cavities once filled by shells, tree branches and other organic material are filled by quartz, opal, agate or carbonate minerals. They are often smaller than volcanic geodes, which are more sought after and form when voids (formed by trapped gases) in basaltic lava flows are filled with agate, quartz and opal.  Much of the material for volcanic geodes is delivered by hydrothermal water or groundwater. There are two major and consistent mentions of geodes in the trilogy. The first is Hoa’s — and, at the very end, Essun’s — chalcedony geode egg, from which stone eaters erupt in their chosen form. The second is Castrima, which serves as a revolutionary space both in terms of its physical use — that is, using a geode as an underground home (and thus leading to the age-old question of: LIVE IN ROCK???) — and in terms of legitimizing the need of orogenes for survival as nobody can physically inhabit Castrima-under unless an orogene is with them.  However, while Castrima is called a geode, the closest possible real life example would likely be the Cave of Crystals in the Naica Mine in Chihuahua, Mexico.  
Cave of Crystals, Naica Mine, Chihuahua, Mexico
    • Shiny (x2)
      • Shiny rocks are not actually a scientific class of rock, but the psychology behind why we like shiny things is interesting. Children, when presented with shiny objects, will usually lick them, showing that there is likely an evolutionary reason behind our enjoyment of shiny objects. A study from the University of Houston shows that there may be a link between shininess and water in our brains, so shiny objects are desirable because they indicate the presence of water, an important tool for survival.
    • Shale
      • Shale is a type of sedimentary rock formed of very small clay particles, which usually have their origins in feldspar. It is the most common sedimentary rock, consisting of almost 75% of the sedimentary rock in the Earth’s crust. This rock doesn’t really feature in the Broken Earth trilogy other than the fact that it is the original form of slate, which they use for building.
    • Pebbles
      • To be scientifically accurate, pebbles are small, smooth rocks. They must be waterworn, giving them a smooth texture, and they can range from 4-64 mm in diameter. The Fulcrum tests orogenes through the shifting of pebbles, so Essun tests Ykka’s skills by having her try to shift pebbles, a test which she fails.  However, later on, Essun realizes, “She can’t shift a pebble, but she can slice out corners and lines so neatly that the end result looks machine-carved… Maybe she couldn’t shift a pebble because who the rust needs to shift pebbles?… Ykka’s way is to simply be precise where it is practical to do so.  Maybe she failed your tests because they were the wrong tests” (Obelisk Gate)
    • Pyrite
      • Pyrite is a mineral that is often mistaken for gold due to its color. However, the two minerals often form together and some pyrite contains enough real gold to warrant mining it. This one does not feature at all in the trilogy.

Based on our research, we have decided to pick new favorite rocks/orogene names for ourselves. Here they are, with justification!

  • Helen: Azurite – This mineral has a weirdly high specific gravity combined with an incredibly low hardness on the Mohs scale which is an unusual combination. Despite the fact that it is pretty, it is generally not used as in jewelry, since it is not durable and will turn into malachite over time (the green part of the above picture). The fussiness and weird physical properties of this mineral appeal to me, as does the fact that its most practical use is as an indicator for copper mines, which has nothing to do with the actual use of the mineral itself. Also, it was the result I got on a which mineral are you quiz (if you don’t take this quiz and comment your mineral did you really read this post?), which as everyone knows, must be 100% accurate. Also, as we learned earlier, psychologically, I am attracted to the shiny, shiny rock. 
    Cut and polished azurite
  • Abby: Opal – Opal is not actually a mineral, but a mineraloid, as it lacks a crystal structure, however, it is still generally categorized with true minerals.  Opals are generally known for their rich and varying color, which occurs due to light refraction in tiny silica spheres within the mineraloid. Some opals, when put under conditions of stress, undergo an effect called crazing (which Helen elaborates upon in her post on the etymology of the word crazy), wherein the opal forms internal and external cracks; crazing lacks consistency and is often unpredictable.  I’m fascinated by this mineral due both to its beauty in its iridescent coloring and due to my own psychological projections onto its qualities.  Additionally, the opal is often mysticized and fabled due to its aesthetics. However, the main exposure I’ve had to opal is in the form of the antagonist of the greatest young adult series of all time: Artemis Fowl. She is my hero, and thus I want to become her.  
Raw opal

P.S. – We are sorry this is so long. ‘Tis the price one must pay for science.  Despite this, we are somewhat proud of its girth.

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