Chemistry:Cafetite
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| Cafetite | |
|---|---|
 | |
| General | |
| Category | oxide mineral |
| Formula (repeating unit) | (Ca,Mg)(Fe,Al)2Ti4O12·4(H2O) |
| Strunz classification | 4.FL.75 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/n |
| Unit cell | a = 4.944 Å, b = 12.109 Å, c = 15.911 Å; β= 98.93°; Z = 8[1] |
| Identification | |
| Color | Pale yellow to colorless |
| Crystal habit | Elongated columnar to acicular crystals, fibrous aggregates, pseudo-orthorhombic |
| Cleavage | Prismatic |
| Tenacity | Brittle |
| Mohs scale hardness | 4–5 |
| |re|er}} | Adamantine |
| Streak | White |
| Diaphaneity | Semitransparent |
| Specific gravity | 3.28 |
| Optical properties | Biaxial (–), 2V=58°, Dispersion very strong, r > v |
| Refractive index | nα = 1.95, nβ = 2.08, nγ = 2.11 |
| Birefringence | δ = 0.16 |
| Pleochroism | none |
| 2V angle | Measured: 38° |
| References | [1][2][3][4] |
Cafetite is a rare titanium oxide mineral with formula (Ca,Mg)(Fe,Al)2Ti4O12·4(H2O). It is named for its composition, Ca-Fe-Ti.[4]
It was first described in 1959 for an occurrence in the Afrikanda Massif, Afrikanda, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia .[3][2] It is also reported from the Khibiny and Kovdor massifs of the Kola Peninsula and from Meagher County, Montana, US.[3]
It occurs in pegmatites in a pyroxenite intrusion as crystals in miarolitic cavities. It occurs associated with ilmenite, titaniferous magnetite, titanite, anatase, perovskite, baddeleyite, phlogopite, clinochlore and kassite.[2]
References
- ↑ 1.0 1.1 Mineralienatlas
- ↑ 2.0 2.1 2.2 Handbook of Mineralogy
- ↑ 3.0 3.1 3.2 Mindat.org
- ↑ 4.0 4.1 Webmineral.com
- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
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