| Crookesite | |
|---|---|
 | |
| General | |
| Category | Selenide mineral |
|
Formula (repeating unit) |
Cu 7( Tl, Ag) Se 4 |
| IMA symbol | Crk [1] |
| 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 | [2] [3] |
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)
2
Se.
[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
- List of minerals
- List of minerals named after people
- Sabatierite – Selenide of copper and thallium
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.
- ^ a b c Webmineral site
- ^ Handbook of Mineralogy
- ^ http://www.mindat.org/min-1159.html Mindat
- 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.
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