Dioptase

Dioptase is a rare cyclosilicate from the silicates and germanates class and highly sought after by collectors because of its spectacular colour.

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Dioptase from Argentina

Origin of name: Firstly mentioned in 1793 by French mineralogist Jean-Claude Delamétherie, who, however, mislead by the colour thought it was a variety of emerald and thus named it Emeraudine.  In 1797 famed French Mineralogist René-Just Haüy renamed it  from the Greek διοπτεία (diopteia) for "through" and "to see" in allusion to the visibility of internal cleavage planes.

Synonyms and trade names: emerald copper

Can be confused with: other deep gren gems like emerald, (chrome-) tourmaline, (chrome-) diopside etc

Localities: at the time of writing (2024) about 180 localities of dioptase are known. 76 deposits are in the Usa, mostly in Arizona and California), 20 in Latin America (Chile und Peru) and more than 40 in Congo. Type locality is Altyn-Tyube in Kazakhstan. Other localities are Argentinia, New Zealanmd, Germany, France, Italy, Iran, Marocco and several more.
Some of the best dioptase comes from Tsumeb, Namibia.

Dioptas from Tsumeb, Namibia

Handling: due to low hardness, perfect cleavage and high sensitivity to heat and acides dioptase is not suited for jewellery use.
Cutting quality dioptase rough is extremely rare and thus faceted dioptase is hardly ever offered in the gem trade.

Worth knowing: dioptase contains water which it can lose when even warmed only moderately. This loss of crystal water can render dioptase dull and dark so keep away from direct sunlight and never ever clean ultrasonically!

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