Cafetite
(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]
2Ti
4O
12·4(H
2O)
(same H-M symbol)
b = 12.109 Å,
c = 15.911 Å;
β= 98.93°; Z = 8[2]
Cafetite is a rare titanium oxide mineral with formula (Ca,Mg)(Fe,Al)
2Ti
4O
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]
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 Mineralienatlas
- ^ a b c Handbook of Mineralogy
- ^ a b c Mindat.org
- ^ a b Webmineral.com
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