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Creedite
| Creedite | |
|---|---|
 | |
| General | |
| Category | Halide mineral |
| Formula (repeating unit) | Ca3Al2(SO4)(F,OH)10•2(H2O) |
| IMA symbol | Cee[1] |
| Strunz classification | 3.CG.15 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Unit cell | a = 13.91 Å, b = 8.58 Å, c = 10 Å; β = 94.4°; Z = 4 |
| Identification | |
| Color | Colorless, white, violet, orange |
| Crystal habit | Generally appears as anhedral to subhedral in matrix; bladelike prismatic and radial, drusy to granular aggregates |
| Cleavage | Perfect on {100} |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 3.5 - 4 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.71 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.461 nβ = 1.478 nγ = 1.485 |
| Birefringence | δ = 0.024 |
| 2V angle | 65° |
| Dispersion | r > v strong |
| References | [2][3][4] |
Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca3Al2SO4(F,OH)10·2(H2O). Creedite forms colorless to white to purple monoclinic prismatic crystals. It often occurs as acicular radiating sprays of fine prisms. It is translucent to transparent with indices of refraction of nα = 1.461 nβ = 1.478 nγ = 1.485. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 2.7.
Creedite was first described in 1916 from the Creede Quadrangle in Mineral County, Colorado. It is a product of intense oxidation of ore deposits.
- ^ 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.
- ^ http://www.mindat.org/min-1151.html Mindat
- ^ http://www.webmineral.com/data/Creedite.shtml Webmineral
- ^ http://rruff.geo.arizona.edu/doclib/hom/creedite.pdf Handbook of Mineralogy
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