| Crookesite | |
|---|---|
 | |
| General | |
| Category | Selenide mineral |
| Formula | Cu 7(Tl, Ag)Se 4 |
| IMA symbol | Crk1 |
| Strunz classification | 2.BD.50 |
| Crystal system | Tetragonal |
| Crystal class | Disphenoidal (4) H-M symbol: (4) |
| Space group | I4 |
| Identification | |
| Color | Lead-gray |
| Crystal habit | As finely divided, disseminated specks, and as small veinlets. |
| Cleavage | Good, two at right angles |
| Fracture | Brittle |
| Mohs scale hardness | 2.5–3 |
| Luster | Metallic |
| Diaphaneity | Opaque |
| Specific gravity | 6.90 |
| References | 23 |
Crookesite is a selenide mineral composed of copper and selenium with variable thallium and silver.
Characteristics
Its chemical formula is reported either as Cu
7(Tl, Ag)Se
4 or (Cu, Tl, Ag)
2Se.4 It is formed by precipitation from hydrothermal fluids, and contains by mass: 16.3% Tl, 47.3% Cu, 2.9% Ag, and 33.6% Se.2
Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the tetragonal system. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 6.9.
Name and discovery
It was discovered in 1866 in Skrikerum, Sweden and named for Sir William Crookes (1832–1919), the discoverer of the element thallium.2
See also
See also
- List of minerals
- List of minerals named after people
- Sabatierite – Selenide of copper and thallium
References
References
- 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.
- Webmineral site
- Handbook of Mineralogy
- "Crookesite". www.mindat.org. Retrieved 2025-12-15.
- Berger, Rolf A.; Sobott, Robert J. (1987). "Characterization of TlCu7S4, a crookesite analogue". Monatshefte für Chemie. 118 (8–9): 967–972. doi:10.1007/BF00815324. S2CID 102058943.
- Berger, R..A. (1987). "Crookesite and sabatierite in a new light. A crystallographer's comment" (PDF). Zeitschrift für Kristallographie. 181 (1–4): 241–249. Bibcode:1987ZK....181..241B. doi:10.1524/zkri.1987.181.1-4.241.