Tollingraben Styria, Austria — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Evansite
Evansite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Al₃(PO₄)(OH)₆·8H₂O.
It crystallizes in the amorphous crystal system. It is a member of the Amorphous structural group.
Key properties: Mohs hardness 3–4; specific gravity 2; White or slightly tinted streak; Vitreous to resinous or waxy luster.
IMA symbol Evn, grandfathered status — known before the IMA’s founding, named in 1864.
Found in a graphite deposit (Gross-Tresny, Czech Republic); in graphitic gneiss (Vatoinandry district, Madagascar); in coal seams (Alabama, USA); a coating in caves, the phosphate derived from guano.
It is found associated with Variscite, allophane, “limonite”.
In honor of Brooke Evans (1797–1862), English mining geologist, Birmingham, England, who provided the first specimens.