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.^[4] Gananite is an isotropic mineral that 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.^[5] Its color in plane-polarized light is blackish-brown, and it does not show pleochroism.

Gananite
General
Category	Halide mineral
Formula	BiF3
IMA symbol	Gan[1]
Strunz classification	3.AC.20
Crystal system	Cubic
Crystal class	Hextetrahedral (43m) H-M symbol: (4 3m)
Space group	P43m
Identification
Color	Brown to black, greenish black
Crystal habit	Aggregates
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	3.5
Luster	Resinous to semimetallic
Streak	Dark grey
Diaphaneity	Subtranslucent to Opaque
Specific gravity	8.928 calculated
Optical properties	Isotropic
Birefringence	N/A
Pleochroism	Non-Pleochroic
References	[2][3]

Discovery and occurrence

It was first described in 1984 for an occurrence in the Laikeng Mining District, Gan County, Ganzhou Prefecture, Jiangxi Province, China.^[4] The name is given for its occurrence in the Southern Ganzhou (Gannan) region of China.^[2] In the Gannan occurrence, the only reported location, it occurs in quartz veins in association with wolframite, native bismuth, bismuthinite, pyrite and chalcopyrite.^[2]

Uses

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