Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine. Its formula is Cu6Si6O18·6H2O (also reported as CuSiO2(OH)2). It has a hardness of 5, the same as tooth enamel. Its specific gravity is 3.28–3.35, and it has two perfect and one very good cleavage directions. Additionally, dioptase is very fragile, and specimens must be handled with great care. It is a trigonal mineral, forming 6-sided crystals that are terminated by rhombohedra.

It is popular with mineral collectors and is sometimes cut into small gems. It can also be pulverized and used as a pigment for painting.

References
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"Dioptase". mindat.org.
"Making Your Own Water-Based Paint". connect.ecuad.ca. Retrieved 2019-03-12.
"Beautiful Green Dioptase / Schöne grüne Dioptase / 美しい緑の翠銅鉱 | GeoRarities". 2021-05-22. Retrieved 2021-05-23.
Mineralogical Record "TSUMEB!" (special issue), Vol. 8, No. 3, May - June 1977. Table of contents Archived 2020-03-18 at the Wayback Machine
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Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7