Research & Medical Tourette Association Annual Scientific Meeting The Tourette Association of America will convene its annual scientific meeting on Thursday, April 20, 2017, at the Bethesda North...
Bort-like heavily twinned diamond from Congo. Bort or boart is a term used in the diamond industry to refer to shards of non-gem-grade/quality diamonds. In the manufacturing and heavy industries, bort is used to describe dark, imperfectly formed/crystallized diamonds of varying levels of opacity.
The chert form of quartz crystals, which is a subset of quartz that contains crystal structures too small to be seen with the human eye, are also used as gemstones. Chert is formed in a variety of colors and can be found in jewelry such as tiger's eye, jasper, citrine, amethyst and onyx gemstones. Quartz is a very hard silicate and is used for onyx jewelry items that require more handling and wear. Learn more about Earth Science