The black fire opal is the official gemstone of Nevada. Opalescence refers to the optical phenomena displayed by the mineraloid gemstone opal (hydrated silicon dioxide). Stones which are opaque or semi-opaque such as opal, turquoise, variscite, etc. CDs on the Opal and Pearl labels reproduce the recordings. Other minerals found on Mars were jarosite, alunite, hematite, opal, and gypsum. The Lightning Ridge Opal and Gem Festival takes place yearly. Most of the precious opal is partial wood replacement. Visible light cannot pass through large thicknesses of the opal. Exchanging Red Eye for Titan Opal, Gren suspects a trap. Iridescence is seen at its best in precious opal. This type of Mexican opal is referred to as a Cantera opal. While Garnett is in the store, the rare Ethiopian black opal Howard has ordered arrives. Originally, Starburst came in the same flavours as Opal Fruits. Recent data suggests that the world supply of precious opal may have changed.