| Dioptase | |
|---|---|
 | |
| General | |
| Category | Cyclosilicates |
| Formula (repeating unit) | Cu6Si6O18·6H2O |
| IMA symbol | Dpt[1] |
| Strunz classification | 9.CJ.30 |
| Crystal system | Trigonal |
| Crystal class | Rhombohedral (3) H-M Symbol: (3) |
| Space group | R3 (No. 148) |
| Unit cell | a = 14.566, c = 7.778 [Å]; Z = 18 |
| Identification | |
| Color | Dark teal, emerald green |
| Crystal habit | Six sided prisms terminated by rhombohedrons to massive |
| Cleavage | Perfect in three directions |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 |
| Luster | Vitreous |
| Streak | Green |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.28–3.35 |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.652 – 1.658 nε = 1.704 – 1.710 |
| Birefringence | δ = 0.052 |
| References | [2][3] |
Dioptase is an intense emerald-green to bluish-green copper cyclosilicate mineral. It is transparent to translucent. Its luster is vitreous to sub-adamantine. Its formula is Cu6Si6O18·6H2O (also reported as CuSiO2(OH)2). It has a hardness of 5, the same as tooth enamel. Its specific gravity is 3.28–3.35, and it has two perfect and one very good cleavage directions. Additionally, dioptase is very fragile, and specimens must be handled with great care. It is a trigonal mineral, forming 6-sided crystals that are terminated by rhombohedra.
It is popular with mineral collectors and is sometimes cut into small gems. It can also be pulverized and used as a pigment for painting.
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ "Dioptase Mineral Data". webmineral.com.
- ^ "Dioptase: Mineral information, data and localities". www.mindat.org.