Dioptase comes from the Greek word DIA which means "through" and OPTOMAI which means "visible". It refers to the mineral's two cleavage directions that are visible inside the unbroken dioptase crystals.

Dioptase is a copper silicate mineral just like chrysocolla.

It is a lustrous emerald-green to bluish-green crystal. It is transparent to translucent and its luster is vitreous to sub-adamantine. It has a hardness of 5 on Mohs hardness scale. This is what distinguishes dioptase from the emerald; emerald is 8 on the Mohs hardness scale. It must be handled with care because it is very fragile.

Dioptase are highly valued and sought after by gem collectors. It is rarely used in jewelry because of its brittle and soft nature. Very few good specimens are cut into small emerald-like gems. Due to the intensity of its colour, it has been used since ancient times as paint pigment.

The use of dioptase as a green pigment can be traced back to Neolithic times, including the famous group of ceramic figures of 'Ain Ghazal dating from the 9th century BC, in today’s Jordan. Three of these thirty-two ritual statues, half-size human figures modelled in white plaster, had their eyes formed with a cowrie shell, a bitumen pupil, highlighted with a vivid green dioptase pigment.

Dioptase is a rare mineral found mostly in desert regions. The finest specimens of dioptase comes from the Tsumeb Mine in Tsumeb, Namibia. Dioptase is also found in the Southwest deserts of the United States specifically in Arizona. There are some gorgeous looking dioptase specimens from Russian, the Congo, Africa and from Argentina where dioptase comes in crystallized quartz, with copper and malachite mixed.

Ancient gemologists believed that gazing at a dioptase would improve the eyesight and wearing dioptase would also benefit those who had neck and throat troubles.