Gananite

Gananite (simplified Chinese: 赣南矿; traditional Chinese: 贛南礦; pinyin: gànnánkuàng) is a rare bismuth fluoride mineral form of bismuth trifluoride with a general formula of BiF3.[3] Gananite is an isotropic mineral, it belongs to the space group P43m. This means that gananite does not show any colors in cross polarized light, because when polarized light passes through it, it does not split into two perpendicular rays. In other words, because gananite is an isometric mineral, it does not exhibit double refraction. Moreover, this tells us that this mineral is not birefringent.[4] Its color in plane-polarized light is blackish-brown, and it does not show pleochroism.

Gananite
General
CategoryHalide mineral
Formula
(repeating unit)		BiF3
Strunz classification3.AC.20
Crystal systemCubic
Crystal classHextetrahedral (43m)
H-M symbol: (4 3m)
Space groupP43m
Identification
ColorBrown to black, greenish black
Crystal habitAggregates
FractureUneven
TenacityBrittle
Mohs scale hardness3.5
LusterResinous to semimetallic
StreakDark grey
DiaphaneitySubtranslucent to Opaque
Specific gravity8.928 calculated
Optical propertiesIsotropic
BirefringenceN/A
PleochroismNon-Pleochroic
References[1][2]

Discovery and occurrence

It was first described in 1984 for an occurrence in the Laikeng Mining District, Gan County, Ganzhou Prefecture, Jiangxi Province, China.[3] The name is given for its occurrence in the Southern Ganzhou (Gannan) region of China.[1] In the Gannan occurrence, the only reported location, it occurs in quartz veins in association with wolframite, native bismuth, bismuthinite, pyrite and chalcopyrite.[1]

Uses

Despite the obscurity of gananite and its very limited use, it is sometimes used in China as a bismuth ore.

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References
  1. "Gananite", Mineral Data Publishing, 2005, accessed 16 December 2010.
  2. Gananite Mineral Data, accessed 16 December 2010.
  3. Gananite, MinDat.org, accessed 16 December 2010.
  4. Jambor, J. L., Burke, E. A., Ercit, T. S., Grice, J. D. (1988) New mineral names. American Mineralogist, 73, 1492-1499.
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