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Formula: Bi4O4(U6+O2)(AsO4)2.2H2O
Hydrated arsenate,
walpurgite group,
bismuth-bearing
uranyl mineral
Crystal System: Triclinic
Specific gravity: 6.59 calculated
Hardness: 3½
Streak: Yellow-white
Colour: Yellow, orange-yellow; colourless to light yellow in transmitted light.
Environments:
Walpurgite is a rare secondary mineral in the oxidised
zone of bismuth-uranium-arsenic-bearing
hydrothermal mineral deposits.
At the type locality, the Weißer Hirsch Mine, Neustädtel, Saxony, Germany, walpurgite is associated with
trögerite, zeunerite,
uranosphaerite,
uranospinite and
torbernite
(Mindat, HOM).
Walpurgite from the Weißer Hirsch Mine -
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At Joachimsthal, Bohemia, Czech Republic, walpurgite is associated with
torbernite
(AM 28: 521).
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