PROFILBARU.COM

Greifensteinite
Greifensteinite
	Greifensteinite (picture size: 3 mm)
General
Category	Phosphate mineral ; Roscherite group
Formula; (repeating unit)	Ca2Fe2+5Be4(PO4)6(OH)4·6H2O
IMA symbol	Gfs
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})
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

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

^ 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.
^ ^a ^b ^c ^d Greifensteinite data on Webmineral
^ Mindat.org
^ Mineralienatlas
^ 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]