Dioptase

Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine.

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, this mineral is very fragile, and specimens must handled with great care. It is a trigonal mineral, forming 6-sided crystals that terminated by rhombohedra.

It is popular with mineral collectors, and it occasionally cut into small emerald-like gems. Dioptase and chrysocolla are the only relatively common copper silicate minerals. A dioptase gemstone should never exposed to ultrasonic cleaning or the fragile gem will shatter. As a ground pigment, it can used in painting.