You will probably never see it in mall jewelry stores. The gem is rare, costly, and the supply is limited. Yet, gem silica is rarely seen in jewelry. Gem silica has been produced occasionally and in limited amounts from locations in New Mexico, Mexico, Peru, Taiwan, and the Philippines.Īs a variety of chalcedony, gem silica has a Mohs hardness of 7 and is durable enough for use in almost any jewelry design. The Keystone Copper Mine in Arizona produced notable amounts of gem silica in the early 1900s. The Miami-Inspiration Mine in Arizona is the best recent source of high-quality gem silica. It is a material produced by the gram rather than by the ton. Deposits are usually small in size and volume. Commonly associated minerals include quartz, chalcedony, chrysocolla, and malachite. Its occurrence, habits, and deposit geometries are like any other type of chalcedony. It is even known to occur as a mineral lining in geodes (see photo on this page). It is a secondary mineral that forms as cavity linings and fracture fillings in the rocks above and adjacent to copper deposits. Gem silica is always associated with copper deposits. Most of these locations have been productive for only a few years before being worked out. Only a few locations have produced noteworthy amounts of gem silica.
Specimen and photo by Arkenstone / Geology of Gem Silica This specimen is approximately 8 x 5.5 x 3.5 centimeters in size. Botryoidal Gem Silica: A beautiful specimen of gem silica in a turquoise blue color, exhibiting the botryoidal habit that is typical of chalcedony.