What is Dioptase?
Dioptase is an intensely emerald-green hydrated copper silicate, famous for transparent trigonal crystals from arid oxidised copper deposits.
Mineralogy and structure
Reference formula: CuSiO3·H2O. Dioptase is a cyclosilicate with six-membered silicate rings. Dioptase is trigonal with the ideal formula CuSiO3·H2O and a six-membered silicate-ring structure. Its perfect cleavage and moderate hardness explain why large transparent crystals are valuable but vulnerable to careless handling. The reference record uses trigonal symmetry. Typical hardness is 5–5 on the Mohs scale and specific gravity is approximately 3.28–3.35.
Colour, lustre and habit
Typical colours include emerald green, blue-green. The usual prismatic, rhombohedral, botryoidal habit and vitreous, sub-adamantine lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Dioptase forms in or is associated with arid oxidation zones of copper-bearing hydrothermal deposits, commonly with chrysocolla, malachite, calcite and quartz. Important documented localities include Kazakhstan, Namibia, the Democratic Republic of the Congo, Chile, Peru and Arizona.
The emerald-green collector favourite
Few minerals match dioptase for pure green intensity. Transparent crystals with sharp rhombohedral form and a documented Kazakhstan or Namibian locality are especially compelling in a cabinet or premium mineral catalogue.
Collecting and care
Dioptase is too brittle and cleavage-prone for everyday jewellery. Protect crystals from impact, heat, acids and vibration; use a secure setting only with specialist advice and keep the specimen away from children and pets.
