Greifensteinite

Greifensteinite
Greifensteinite (picture size: 3 mm)
General
Category Phosphate mineral
Roscherite group
Formula
(repeating unit)		 Ca2Fe2+5Be4(PO4)6(OH)4·6H2O
Strunz classification 8.DA.10
Dana classification 42.7.7.4
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/c
Unit cell a = 15.903, b = 11.885
c = 6.677 [Å]; β = 94.68°; Z = 2
Identification
Color Yellow green, olive green, light brown
Crystal habit Prismatic
Cleavage Good on {100} (or parting on {100})[1]
Fracture Uneven
Tenacity brittle
Mohs scale hardness 4.5
Luster Vitreous
Streak White, greenish
Diaphaneity Transparent to translucent
Specific gravity 2.93
Optical properties Biaxial (-)
Refractive index nα: 1.624
nβ: 1.634
nγ: 1.638
Birefringence 0.014
2V angle 80°
References [1][2][3]

Greifensteinite is beryllium phosphate mineral with formula: Ca2Fe2+5Be4(PO4)6(OH)4·6H2O. It is the Fe2+ dominant member of the roscherite group.[4] It crystallizes in the monoclinic crystal system and typically forms prismatic dark olive green crystals.[1]

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.[1]

References

  1. 1 2 3 4 Greifensteinite data on Webmineral
  2. ↑ Mindat.org
  3. ↑ Mineralienatlas
  4. ↑ 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
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