Greifensteinite
(repeating unit)Ca2Fe2+5Be4(PO4)6(OH)4·6H2O IMA symbol Gfs[1] 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})[2] 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 [2][3][4]
(same H-M symbol)
c = 6.677 [Å]; β = 94.68°; Z = 2
nβ: 1.634
nγ: 1.638
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
- 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]