Cafetite | |
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General | |
Category | oxide mineral |
Formula (repeating unit) | (Ca,Mg)(Fe,Al) 2Ti 4O 12·4(H 2O) |
IMA symbol | Cft [1] |
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 [2] |
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 |
Luster | 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 | [2] [3] [4] [5] |
Cafetite is a rare
titanium
oxide mineral with formula (
Ca,
Mg)(
Fe,
Al)
2
Ti
4
O
12·4(
H
2O). It is named for its composition, Ca-Fe-Ti.
[5]
It was first described in 1959 for an occurrence in the Afrikanda Massif, Afrikanda, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia. [4] [3] It is also reported from the Khibiny and Kovdor massifs of the Kola Peninsula and from Meagher County, Montana, US. [4]
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. [3]