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Cafetite

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Cafetite
Yellow cafetite crystals with green lizardite and calcite
General
Categoryoxide mineral
Formula
(repeating unit)
(Ca,Mg)(Fe,Al)
2
Ti
4
O
12
·4(H
2
O)
IMA symbolCft[1]
Strunz classification4.FL.75
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/n
Unit cella = 4.944 Å,
b = 12.109 Å,
c = 15.911 Å;
β= 98.93°; Z = 8[2]
Identification
ColorPale yellow to colorless
Crystal habitElongated columnar to acicular crystals, fibrous aggregates, pseudo-orthorhombic
CleavagePrismatic
TenacityBrittle
Mohs scale hardness4–5
LusterAdamantine
StreakWhite
DiaphaneitySemitransparent
Specific gravity3.28
Optical propertiesBiaxial (–), 2V=58°, Dispersion very strong, r > v
Refractive indexnα = 1.95, nβ = 2.08, nγ = 2.11
Birefringenceδ = 0.16
Pleochroismnone
2V angleMeasured: 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
2
O)
. 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

[edit]
  1. ^ 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.
  2. ^ a b Mineralienatlas
  3. ^ a b c Handbook of Mineralogy
  4. ^ a b c Mindat.org
  5. ^ a b Webmineral.com