Dioptase from Aztyn-Tyube Mine, Karagandy Province, Kazakhstan (No.56)

Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral.

It has a hardness of 5, the same as tooth enamel.

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.

Late in the 18th Century, cooper miners at the Altyn-Tyube mine, Karagandy Province, Kazakhstan. They thought they had found emerald deposits of their dreams. Finding fantastic cavities in quartz veins in a limestone, filled with thousands of lustrous emerald-green transparent crystals. The crystals were sent to Moscow, Russia for analysis. However the mineral's inferior hardness of 5 compared with emerald's greater hardness of 8 easily distinguished it.

Later famed French mineralogist, Rene Just Hauy in 1797 determined that the enigmatic Altyn-Tyube mineral was to science and name it Dioptase. (Greek, dia, "through” and optima, "Vision”)  alluding to the mineral's two cleavage directions that are visible inside unbroken crystals.

Dioptase is an uncommon mineral found mostly in desert regions where it forms as a secondary mineral in the oxidised zone of copper sulphide mineral deposits.

The Altyn Tube mine in Kazakhstan still does provides handsome specimens; a brownish quartzite host distinguishes its specimens from other localities. The finest specimens of all were found at the Tsumeb Mine in Tsumeb, Namibia.

Dioptase is also found in the deserts of the southwestern USA, and an interesting occurrence is the Malpaso Quarry in and near Agua de Oro Argentina.