Black onyx is the name given to a black translucent form of chalcedony ( pronounced "kal · SED · nee" ). Chalcedony is a form of silica, therefore it is similar to the quartz family of minerals. The difference between quartz and chalcedony is the crystal formation.
Chalcedony is made up of tiny microscopic crystals, or microcrystalline. Quartz crystal are larger, ranging from clusters of tiny points on a rocks surface, to huge single crystals. Amethyst and citrine are both forms of quartz.
Chalcedony and quartz are both clear colored minerals. Silica is a clear mineral, the different colors we see in the various gemstones come from impurities in the stone. In the case of black onyx, carbon is usually the mineral creating the dark color.
Black onyx is a hard durable gemstone that takes an exceptional polish. Black onyx is also colorfast, therefore it will not fade or change colors.
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