- Crookesite
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Crookesite General Category Selenide mineral Chemical formula Cu7(Tl,Ag)Se4 Strunz classification 02.BD.50 Identification Color Lead-gray Crystal habit As finely divided, disseminated specks, and as small veinlets. Crystal system Tetragonal - Disphenoidal Cleavage Good, two at right angles Fracture Brittle Mohs scale hardness 2.5–3 Luster Metallic Diaphaneity Opaque Specific gravity 6.90 References [1][2] Crookesite is a selenide mineral composed of copper and selenium with variable thallium and silver.
Contents
Characteristics
Its chemical formula is reported either as Cu7(Tl,Ag)Se4 or (Cu,Tl,Ag)2Se.[3] 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.[1]
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.[1]
See also
References
- Berger, Rolf A.; Sobott, Robert J. (1987). "Characterization of TlCu7S4, a crookesite analogue". Monatshefte für Chemie Chemical Monthly 118: 967. doi:10.1007/BF00815324.
- Berger, R..A. (1987). "Crookesite and sabatierite in a new light A crystallographer's cornrnent". Zeitschrift für Kristallographie 181: 241–249. doi:10.1524/zkri.1987.181.1-4.241. http://rruff.geo.arizona.edu/doclib/zk/vol181/ZK181_241.pdf.
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