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Greifensteinite

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Greifensteinite
Greifensteinite (picture size: 3 mm)
General
CategoryPhosphate mineral
Roscherite group
Formula
(repeating unit)
Ca2Fe2+5Be4(PO4)6(OH)4·6H2O
IMA symbolGfs[1]
Strunz classification8.DA.10
Dana classification42.7.7.4
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 15.903, b = 11.885
c = 6.677 [Å]; β = 94.68°; Z = 2
Identification
ColorYellow green, olive green, light brown
Crystal habitPrismatic
CleavageGood on {100} (or parting on {100})[2]
FractureUneven
Tenacitybrittle
Mohs scale hardness4.5
LusterVitreous
StreakWhite, greenish
DiaphaneityTransparent to translucent
Specific gravity2.93
Optical propertiesBiaxial (-)
Refractive indexnα: 1.624
nβ: 1.634
nγ: 1.638
Birefringence0.014
2V angle80°
References[2][3][4]

Greifensteinite is beryllium phosphate mineral with formula: Ca2Fe2+5Be4(PO4)6(OH)4·6H2O. It is the Fe2+ dominant member of the roscherite group.[5] It crystallizes in the monoclinic crystal system and typically forms prismatic dark olive green crystals.[2]

It was first described in Germany at Greifenstein Rocks, Ehrenfriedersdorf, and was named for the location. At the type locality, it occurs within a lithium-rich pegmatite in miarolitic cavities. It was approved by the International Mineralogical Association in 2002.[2]

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 c d Greifensteinite data on Webmineral
  3. ^ Mindat.org
  4. ^ Mineralienatlas
  5. ^ Roscherite group on Mindat.org
  • Rastsvetaeva R K, Gurbanova O A, Chukanov N V (2006) Crystal structure of greifensteinite Ca2Fe2+☐Mg2Fe2+2Be4(PO4)6(OH)4·6H2O. Doklady Chemistry 41, 18-25 [1]