Judging quality
Soft for its brilliance and with perfect cleavage; crystals are short rhombohedral prisms. Emerald is much harder and never grows in these crusted plates.
Silicate
Dioptase
Perhaps the most intensely green mineral there is — copper silicate crystals of a saturated emerald so vivid that eighteenth-century collectors assumed they had found an emerald deposit. Tsumeb specimens on white dolomite are the benchmark.
Care
Fragile, cleavable and light-stable but knock-sensitive. Dry dusting only, never ultrasonic.
History & lore
The name comes from Greek for 'see through', because the internal cleavage planes are visible inside the crystal.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Dioptase
- What is Dioptase?
- Perhaps the most intensely green mineral there is — copper silicate crystals of a saturated emerald so vivid that eighteenth-century collectors assumed they had found an emerald deposit. Tsumeb specimens on white dolomite are the benchmark.
- How hard is Dioptase and what is it made of?
- Dioptase is a Silicate-family mineral with the composition CuSiO3·H2O. It crystallizes in the trigonal system and rates 5 on the Mohs hardness scale. It occurs in emerald green, green, blue-green.
- Where does Dioptase come from?
- Notable localities for Dioptase include Tsumeb, Namibia, Republic of the Congo (Mindouli), Kazakhstan, Arizona, USA.
- How do you tell good Dioptase from filler?
- Soft for its brilliance and with perfect cleavage; crystals are short rhombohedral prisms. Emerald is much harder and never grows in these crusted plates.
- How do you care for Dioptase?
- Fragile, cleavable and light-stable but knock-sensitive. Dry dusting only, never ultrasonic.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.