Acuminite

Acuminite
General
CategoryHalide mineral
Formula
(repeating unit)
SrAlF4OH·(H2O)
IMA symbolAcu[1]
Strunz classification3.CC.10
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 13.223, b = 5.175
c = 14.251 [Å]; β = 11.61°; Z = 8
Identification
ColorWhite
Crystal habitClusters of acute dipyramidal Spearhead shaped crystals
TwinningContact on {100}
CleavagePerfect on {001}
Mohs scale hardness3.5
LusterVitreous
DiaphaneityTransparent
Specific gravity3.295
Optical propertiesBiaxial (+)
Refractive indexnα = 1.451 nβ = 1.453 nγ = 1.462 - 1.463
References[2][3][4]

Acuminite is a rare halide mineral with chemical formula: SrAlF4(OH)·(H2O). Its name comes from the Latin word acumen, meaning "spear point". Its Mohs scale rating is 3.5.

Acumenite has only been described from its type locality of the cryolite deposit in Ivigtut, Greenland.[2]

See also

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References

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  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 Handbook of Mineralogy
  3. ^ Mindat.org
  4. ^ Webmineral data