Some minerals form deep in the earth, but not quartz. Quartz often forms on or near the surface, crystallizing out of very hot water heated by geological events in which it was dissolved.
When the silica is dissolved in water, it can penetrate other minerals and organic matter, replacing much of the original material over long periods of time before crystallizing. Thus the form and shape of the original material is preserved as the object becomes almost solid quartz. Many fossils are made this way, with quartz gradually replacing the organic material. In rare instances the silica forms as precious opal rather than quartz crystal. Petrified wood and dinosaur bone are also often mainly quartz or, rarely, opal.
Tiger eye (or tiger’s eye) is a fibrous asbestos-like mineral called crocidolite that has become encased and largely replaced by quartz, the parallel fibrous strands creating a golden color with a chatoyant-type optical effect in it.
Red tiger’s eye is commonly the result of dyeing normal tiger’s eye. The dye enters the fine channels in the quartz that were once filled with crocidolite. Red tiger’s eye may also be made by heating some tiger’s eye where iron oxide has partially filled the channels in the quartz.
Tiger’s eye is never synthesized commercially but poor quality fakes are found in the market.
Tiger’s eye is a unique and attractive gemstone mainly mined in South Africa.
Image courtesy of greatrough.com.
Sign up to be notified of new products, member-only sales, and announcements.