Woodhouseite

Woodhouseite belongs to the beudantite group AB3(XO4)(SO4)(OH)6 where A = Ba, Ca, Pb or Sr, B = Al or Fe and X = S, As or P. Minerals in this group are isostructural with each other and also with minerals in the crandallite and alunite groups. They crystallise in the rhombohedral system with space group R3m and crystals are usually either tabular {0001} or pseudo-cubic to pseudo-cuboctahedral. Woodhouseite was named after Professor Charles Douglas Woodhouse[4] (1888–1975), an American mineralogist and mineral collector from the University of California, Santa Barbara, US, and one-time General Manager of Champion Sillimanite, Inc.

Woodhouseite
Woodhouseite from the type locality, the Champion Mine, Mono County, California, US. Specimen width is 2.8 cm
General
CategoryPhosphate minerals
Formula
(repeating unit)		CaAl3(SO4)(PO4)(OH)6
Strunz classification8.BL.05
Dana classification43.04.01.08
Crystal systemTrigonal
Crystal classHexagonal scalenohedral (3 2/m)
Identification
Formula mass414.10 g/mol
ColorWhite, flesh-pink or colorless
Crystal habitCrystals small, pseudocubic rhombohedral {1012}; tabular at times {0001}, with curved and striated faces.
CleavageExcellent on {0001}
Mohs scale hardness4.5
LusterVitreous, pearly on {0001}
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity(measured): 3.012 (calculated): 3.00
Optical propertiesUniaxial (+), 2V = 0° to 20°
Refractive index(AM22) nω = 1.636
nε = 1.647
Birefringenceδ = 0.011
SolubilitySoluble in acids only after driving off the water in a closed tube.
Other characteristicsNot radioactive.
References[1][2][3]

Environment

Woodhouseite is a secondary mineral found where wall rock alteration occurred in hydrothermal and disseminated ore deposits; rare in cave deposits, formed from guano. At the type locality it occurs in vugs in quartz veins in an andalusite, Al2OSiO4, deposit. This is in pre-Cambrian meta-quartzite that has been intruded by late Jurassic granitic rocks. Woodhouseite is found only near masses of lazulite, MgAl2(PO4)2(OH)2. Associated Minerals at the type locality include topaz, Al2SiO4F2, quartz, SiO2, augelite, Al2PO4(OH)3, lazulite, MgAl2(PO4)2(OH)2, tourmaline, baryte, BaSO4, muscovite, KAl2(Si3Al)O10(OH)2, and pyrophyllite, Al2Si4O10(OH)2, all of which formed before the woodhouseite, which is a late-forming mineral.[5]

Localities

The type locality is the Champion Mine (White Mountain Mine), White Mountain, Laws, White Mountains, Mono County, California, US. This is a former sillimanite mine located near Laws; mineralisation is a metamorphic sillimanite deposit hosted in quartzite.

Structure

Space Group: R3 2/m
Unit Cell Parameters: a = 6.993 Å, c = 16.386 Å, Z: 3

References
  1. http://www.webmineral.com/data/Woodhouseite.shtml
  2. http://www.mindat.org/min-4311.html Mindat.org
  3. http://rruff.geo.arizona.edu/doclib/hom/woodhuseite.pdf Handbook of Mineralogy
  4. http://content.cdlib.org/view?docId=hb1199n68c&doc.view=frames&chunk.id=div00099&toc.depth=1&toc.id=&brand=calisphere
  5. Lemmon, Dwight M (1937) American Mineralogist 22:939-948
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