Allanpringite
Appearance
Allanpringite | |
---|---|
General | |
Category | Phosphate mineral |
Formula (repeating unit) | Fe3+3(PO4)2(OH)3·5H2O |
Strunz classification | 08.DC.50 |
Dana classification | 42.10.02.02 |
Space group | Monoclinic – prismatic, H-M symbol (2/m), space group P21/n |
Unit cell | a = 9.777 Å, b = 7.358 Å, c = 17.83 Å, Z = 4; β = 92.19° |
Identification | |
Formula mass | 498.07 g |
Color | Pale brownish yellow |
Crystal habit | Acicular |
Cleavage | {hk0} perfect, {010} good |
Fracture | Irregular/uneven |
Tenacity | Brittle |
Mohs scale hardness | 3 |
Luster | Vitreous |
Streak | Pale yellowish white |
Diaphaneity | Translucent to transparent |
Specific gravity | 2.54 (meas.), 2.583 (calc.) |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.662 nβ = 1.675 nγ = 1.747 |
Birefringence | 0.085 |
2V angle | 48° (calc.) |
References | [1][2] |
Allanpringite is a phosphate mineral named after Australian mineralogist Allan Pring, South Australian Museum. Allanpringite is a Fe3+ analogue Al-phosphate mineral wavellite, but it has a different crystal symmetry – monoclinic instead of orthorhombic in wavellite. It forms needle-like crystals, which are always twinned and form parallel bundles up to about 2 mm long. They are often found in association with other iron phosphates in abandoned iron mines.[1][3]
References
- ^ a b Allanpringite. Mindat
- ^ Allanpringite. Webmineral
- ^ Kolitsch, U., Bernhardt, H.J., Lengauer, C.L., Blass, G., and Tillmanns, E., 2006. Allanpringite, Fe3(PO4)2(OH)3·5H2O, a new ferric iron phosphate from Germany, and its close relation to wavellite. European Journal of Mineralogy 18, 793-801