Dioptase is an intense emerald-green to bluish-green mineral that is cyclosilicate of copper. It is transparent to translucent.

Additionally, dioptase is very fragile, and specimens must be handled with great care. It is a trigonal mineral, forming six-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.