Dioptase

Dioptase is an extremely attractive mineral, known for its rich emerald green to blue-green color. As a hydrated copper silicate, it often forms magnificent clusters of bright, well-formed prismatic crystals, although it can also occur as solid masses or drusen crusts. Its crystals, which are transparent to translucent, have a bright vitreous luster and perfect rhombohedral cleavage in three directions. With a hardness of 5 on the Mohs scale, dioptase is a relatively soft and rather brittle mineral. These characteristics make it unsuitable for most jewelry, where the stone may be subjected to impact or friction.

However, it is precisely because of its beauty and perfect crystal forms that dioptase is highly prized as a collector's mineral. The name of the mineral, derived from the Greek words "dia" (through) and "optos" (visible), was given by the famous French mineralogist René Juste Gaillaud in the late 18th century. The name refers to the ability to see the internal cleavage planes through transparent crystals. The most famous and valuable specimens of dioptase historically come from the Altyn-Tyube deposit in Kazakhstan, which is famous for its large, clearly cut crystals of exceptional quality and transparency. Other important finds are known from Tsumeb (Namibia), Arizona (USA), the Republic of the Congo and Chile.

Specimens from different locations may vary in crystal size and color intensity. Due to its intense color, aesthetically pleasing crystal forms and the relative rarity of high-quality specimens, dioptase is a desirable and valuable exhibit in mineralogical collections around the world.