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Formula: Al3(PO4)(OH)6.8H2O
Hydrated phosphate containing hydroxyl
Crystal System: Amorphous
Specific gravity: 1.8 to 2.2 measured
Hardness: 3 to 4
Streak: White, lightly tinted
Colour: Colourless, milk-white, lightly tinted blue, green or yellow at times; brown,
reddish-brown, or red due to wüstite inclusions; colourless
to brown in transmitted light
Solubility: Easily soluble in acids
Common impurities: Cu,Pb
Environments:
Evansite is a secondary phosphate mineral that
forms as a derivative of guano, usually in the form
of cave fillings in graphite-containing deposits,
gneiss and coal strata. Associated minerals include
variscite,
allophane and
limonite (Wiki).
In the past there has been some discussion about whether evansite and
bolivarite are in fact the same mineral, but they are now accepted as
distinct species
(CM 33.59-65).
Localities
In the phosphate deposits of South Australia, evansite is usually associated with
apatite,
wavellite or turquoise
(AJM 17.1.16).
At the type locality, the Železník iron deposit, Sirk, Revúca District, Banská Bystrica Region, Slovakia,
evansite occurs as incrustations in cavities in limonite, as
small reniform or globular stalactites and pearl-like growths. Associated minerals include
variscite, limonite and
allophane
(Mindat).
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