metavauxite

metavauxite

[¦med·ə′vȯk‚sīt]
(mineralogy)
FeAl2(PO4)2(OH)2·8H2O A colorless mineral composed of hydrous basic phosphate of iron and aluminum; similar to vauxite, but with more water.
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Also at the Main Show, Brian Kosnar of Mineral Classics (Minclassics@aol.com) was showing off a few matrix slabs--wide, thin pieces of matrix range from 5 to 30 cm across--of hard quartz porphyry thickly coated with powder-blue microcrystals of vauxite, together with sparser microcrystals of paravauxite and metavauxite. On some specimens, the blue vauxite forms casts after vanished spherical aggregates of wavellite to 8 mm diameter, and one specimen even shows metallic black microcrystals of franckeite.
Vaux (vauxite, metavauxite, paravauxite; nephew of William S.), Edgar T.
It is the type locality for five mineral species (vauxite, metavauxite, paravauxite, sigloite and jeanbandyite) and has also produced some of the world's best specimens of stannite, cylindrite, monazite, bismoclite, and other species.
Pale orange, transparent, resinous masses of evansite, much resembling tree resin, are occasionally found in association with metavauxite.
It was the principal gangue mineral in some of the richest cassiterite veins mined in the 1920's, and is considered to be the precursor from which the extensive suite of other phosphates (vauxite, paravauxite, metavauxite, wavellite, variscite, crandallite, childrenite, vivianite and allophane) developed, except for monazite and xenotime.
Metavauxite Fe[Al.sub.2](P[O.sub.4])[.sub.2](OH)[.sub.2] 8[H.sub.2]O
Metavauxite was described by Gordon (1944) as being colorless, white, or pale greenish white.
Metavauxite always occurs on wavellite, which encrusts brecciated fragments of porphyry along faults cutting the veins.
Bandy (1944) noted that metavauxite is relatively abundant as loose silky masses in open fractures along a branch of the San Jose vein, on Level 446.
It is the most common of the three "vauxites" (the other being metavauxite) and sometimes forms large masses of crystals in vugs.
Of particular interest are assemblages such as rose-pink monazite-tourmaline-cassiterite-quartz; complexly twinned red greenockite with wavellite; childrenite with vauxite, paravauxite, and wavellite; wavellite with fluorapatite; and vauxite with metavauxite. Fine suites of pyrite, arsenopyrite, tetrahedritetennantite, wurtzite, stannite, vivianite, and cassiterite reflect a wide variety of crystal forms and habits.
Llallagua phosphates, including childrenite, crandallite, fluorapatite, metavauxite, monazite, paravauxite, sigloite, vauxite, vivianite and wavellite, were actively collected by Bandy.