Dioptase
Dioptase is a silicate mineral recognized among collectors for its crystal form and distribution.
About Dioptase
Dioptase is classified as a silicate mineral in the dioptase group and has the chemical formula CuSiO₃·H₂O. It crystallizes in the trigonal system and holds a steady position among silicate species. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
Identification & care
Specimens usually show short prismatic rhombohedral crystals; commonly on matrix. Its color is typically emerald green to blue-green. The luster is sub-adamantine, vitreous, sub-vitreous, the streak is green, and specimens range from transparent to translucent. The cleavage is perfect rhombohedral {1011} in 3 directions. The fracture is conchoidal, which aids identification.
Collector context
How it forms
In terms of geology, Dioptase forms in secondary mineral in oxidized zones of copper ore deposits. It is commonly found in association with wulfenite, malachite, calcite, chrysocolla, shattuckite.
Why collectors care
Dioptase is a frequently-sought species in serious collections because its habit is recognizable, its color often strong, and its best examples unmistakable even at a distance. Chinese material has driven much of the recent visual shift in the species — sharper crystals, deeper colors, cleaner matrix.
What affects value
Value in Dioptase is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.
Naming history
The name Dioptase has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.
Available Dioptase specimens
Dioptase Crystal Cluster, Republic of Congo
Dioptase Crystal Cluster, Democratic Republic of Congo
Dioptase on Matrix, Morocco
Dioptase Crystal Specimens – Three-Piece Set, Congo
Dioptase Crystal on Matrix – Congo
Dioptase Cluster on Limonite Matrix – Congo, DRC
