Santabarbaraite

Santabarbaraite
Santabarbaraite (pseudomorph) after vivianite
General
CategoryPhosphate minerals
Formula
(repeating unit)		Fe3+3(PO4)2(OH)3·5H2O
IMA symbolSbb[1]
Strunz classification8.CE.80
Crystal systemAmorphous
Identification
ColorBrown to light brown
Crystal habitElongated or flattened prisms
TwinningNone
CleavageNone, parting along {010} of replaced phase
FractureConchoidal
Mohs scale hardnessNot determined
LusterVitreous to greasy
Streakyellow-umber
DiaphaneityTranslucent
Specific gravity2.24
Optical propertiesisotropic
Refractive indexn = 1.659
Other characteristicsPseudomorphism
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]

Physical properties

Due to pseudomorphism, Santabarbaraite samples show elongated and flattened prism habits. The bulk crystal color is brown to light brown, but appears yellow brown when viewed under an optical microscope. The streak color of the mineral is yellow-umber.[4] Santabarbaraite has a vitreous-to-greasy luster and shows no fluorescence under ultraviolet light. It is translucent and shows good parting along the cleavage of its original mineral vivianite at {010}. Santabarbaraite's density is 2.24 g/cm3. The mineral is isotropic, with refractive index n=1.659.[4]

Taxonomy

Santabarbaraite is named after Santa Barbara, a mining district in Italy where, in 2000, the mineral was discovered and first described. The district name honors the saint of miners, Saint Barbara,[4] which by association, makes santabarbaraite one of few minerals bearing the name of a woman.

Geologic occurrence

Santabarbaraite occurs in several places. It occurs in the Valderno Superiore lignite-bearing basin in the Santa Barbara mining district, Tuscany, Italy.[4] Santabarbaraite samples may be seen in Victoria, Australia, underlying Pliocene basalt beneath Wannon Falls.[4] It also is found in samples from Lake Baikal, Siberia.[5]

Biological occurrence

Since its discovery in 2000, this mineral hydrate has been found in the teeth of a living organism, the Gumboot chiton.[7][8]

References

  1. ^ 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.
  2. ^ "Santabarbaraite: Mineral information, data and localities". Archived from the original on 7 January 2015. Retrieved 8 December 2007.
  3. ^ "Santabarbaraite Mineral Data". www.webmineral.com. Archived from the original on 1 October 2007. Retrieved 8 December 2007.
  4. ^ a b c d e f g h Pratesi G., Cipriani C., Guili G., and Birch W. D. (2003) Santabarbaraite: a new amorphous phosphate mineral. European Journal of Mineralogy.15, 185–192
  5. ^ a b c 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
  6. ^ 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
  7. ^ Athens, Emily (31 May 2021). "How the 'Wandering Meatloaf' Got Its Rock-Hard Teeth". The New York Times. Archived from the original on 31 May 2021. Retrieved 31 May 2021.
  8. ^ "Persistent polyamorphism in the chiton tooth: From a new biomineral to inks for additive manufacturing | PNAS". Archived from the original on 6 June 2021. Retrieved 6 June 2021.