| Santabarbaraite | |
|---|---|
 Santabarbaraite (pseudomorph) after vivianite | |
| General | |
| Category | Phosphate minerals |
| Formula (repeating unit) | Fe3+3(PO4)2(OH)3·5H2O |
| IMA symbol | Sbb[1] |
| Strunz classification | 8.CE.80 |
| Crystal system | Amorphous |
| Identification | |
| Color | Brown to light brown |
| Crystal habit | Elongated or flattened prisms |
| Twinning | None |
| Cleavage | None, parting along {010} of replaced phase |
| Fracture | Conchoidal |
| Mohs scale hardness | Not determined |
| Luster | Vitreous to greasy |
| Streak | yellow-umber |
| Diaphaneity | Translucent |
| Specific gravity | 2.24 |
| Optical properties | isotropic |
| Refractive index | n = 1.659 |
| Other characteristics | Pseudomorphism |
| References | [2][3] |
Santabarbaraite is an amorphous ferric hydroxy phosphate mineral hydrate that was discovered in Tuscany, Italy during 2000.[4] It also can be found in Victoria, Australia and Lake Baikal, Siberia.[5]
This phosphate mineral has a simplified formula Fe3+3(PO4)2(OH)3·5H2O,[4] which is the same formula of another non-amorphous phosphate mineral called allanpringite.[6] Santabarbaraite occurs as pseudomorphic masses after vivianite (Fe2+3(PO4)2·8H2O). In the process, monoclinic vivianite oxidizes to form the amorphous santabarbaraite.[4] Pseudomorphism may be seen in Victoria, Australia, in Wannon Falls (originally a well-known locality for vivianite). It also may be seen at Lake Baikal, Siberia where the oxidized santabarbaraite may be seen as a rim surrounding vivianite due to exposure to air.[5]
- ^ 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.
- ^ "Santabarbaraite: Mineral information, data and localities". Archived from the original on 7 January 2015. Retrieved 8 December 2007.
- ^ "Santabarbaraite Mineral Data". www.webmineral.com. Archived from the original on 1 October 2007. Retrieved 8 December 2007.
- ^ a b c Pratesi G., Cipriani C., Guili G., and Birch W. D. (2003) Santabarbaraite: a new amorphous phosphate mineral. European Journal of Mineralogy.15, 185–192
- ^ a b Fagel N., Alleman L. Y., Granina L., Hatert F., Thamo-Bozso E., Cloots R. and Andre L. (2005) Vivianite formation and distribution in Lake Baikal sediments. Global and Planetary Change.46, 315–336
- ^ 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