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Dioptase

by Dave Jacobson

Dioptase is a hydrated copper silicate, CuSiO3-H2O. It is a silicate mineral, subclass cyclosilicates. Dioptase is one of my favorite copper minerals due to the beautiful green color of the crystals. Dioptase is found in the oxidation zone of copper deposits and in cavities in the rock associated with those deposits. It is a minor ore of copper. But it is primarily used as a mineral specimen. Some associated minerals are dolomite, calcite, cerussite, limonite, chrysocolla and other copper minerals. Noted specimens have been found in Tsumeb, Nambia and Zaire in Africa. In the USA it is found in California and Arizona. Other noted locations in the world are in Chile and Russia.

Dioptase is in the hexagonal crystal system. Typically it is found in stubby, prismatic, bright emerald green crystals with rhombohedral terminations. It also is found as a crust and in massive forms. Crystals are transparent to translucent with a vitreous luster. Color is dark green. Streak is a pale greenish blue. It is brittle with a conchoidal fracture. Specific Gravity is 3.3 to 3.4. Hardness is 5 which is harder than most copper minerals. It is soluble in hydrochloric acid, staining the solution blue.

Dioptase takes its name from the Greek dia and optazein meaning “to see through”.

I used the following reference materials in preparing this article.

Field Guide To Rocks And Minerals by Frederick H. Pough.

Mineralogy For Amateurs by John Sinkankas. Simon & Schuster's Guide to Rocks And Minerals. The Audubon Society Field Guide

To North American Rocks and Minerals. Amethyst Galleries Mineral Gallery on the internet (http://mineral.galleries.com).

via WSMC newsletter 02/13; CMS eTumbler 02/13, The Quarry, 12/12; from Canaveral Moonstone, 10/12