A variety known as chiastolite has grains of graphite concentrated into a cross-shaped feature.Īnt hill garnet is a novelty gem that ants excavate, haul to the surface and deposit on their ant hill. Their fossilized shells are often cut and used as organic gems.Īndalusite is a metamorphic mineral that is strongly pleochroic and an underappreciated gem. All of the world's production of this organic gem is from a small area in Alberta, Canada.Īn extinct group of marine invertebrate animals that produced a chambered shell. It produces a bright flash of color that rivals opal and labradorite. It is commercially produced at only one mine in the world, located in eastern Bolivia.Īmmolite is a trade name used for iridescent ammonite shell. The color combination is caused by twinning. It is found in many locations around the world.Īmetrine is a bicolor quartz that is half AMEthyst and half ciTRINE. It is one of the most popular faceted gemstones and is sometimes cut en cabochon. It is an organic gem easily cut and polished into bright, lightweight gems.Īmethyst is a transparent variety of quartz that ranges from light lilac to deep purple in color. It usually has a yellowish to orangish brown color but can be white, greenish, bluish, or black. It has a Mohs hardness of 6 with perfect cleavage, so it is best used where it will not suffer abrasion or impact.Īmber is a fossil resin secreted by ancient trees. For that reason, it is common in jewelry.Īmazonite is a trade name given to a light green to bright green variety of microcline feldspar. It is a popular gem cut into cabochons, beads, and ornamental objects.Īlmandine garnet, also known as "almandite," is an iron-rich, red-to-purple garnet that is geologically very common and typically sells on the more affordable side of the garnet price range. It sometimes has a fibrous texture that produces a strong cat's-eye.Īgate is a cryptocrystalline quartz that is translucent and patterned with bands, plumes, dendrites, or inclusions that produce a colorful, interesting appearance. Actinolite is green to grayish green mineral of the amphibole group found in metamorphic rocks.
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