The Mineral WALPURGITE

Chemistry: (BiO)₄UO₂(AsO₄)₂ - H₂O , Hydrated Bismuth Uranyl Arsenate Oxide
Class: Phosphates
Subclass: Arsenates
Uses: A very minor ore of uranium and bismuth and as mineral specimens.
Specimens

Walpurgite is a chemical oddball of a mineral. Not only does it have arsenic and uranium in its chemistry, but bismuth too! The bismuth in walpurgite gives this mineral its unusually high density (SG=5.9) and luster (adamantine). It is too rare to really be considered an ore of either uranium or bismuth, but no doubt some walpurgite has gone into the processing with other ores.

Walpurgite specimens can have attractive tiny clusters of bladed radiating crystals. The mineral gets its name from the Walpurgis Vein at its type locality, Weisser Hirsh Mine, Schneeberg, Saxony, Germany. Remember, this is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.

PHYSICAL CHARACTERISTICS:

Color is typically yellow but can be a reddish orange.
Luster is adamantine to greasy.
Transparency: Crystals are translucent to rarely transparent.
Crystal System is trigonal.
Crystal Habits include platy elongated crystals often aggregated and twinned. Also as crusts, fibrous and earthy.
Cleavage is perfect.
Fracture is lamellar.
Hardness is 3.5
Specific Gravity is approximately 5.95 - 6.69 (well above average for translucent minerals)
Streak is a pale yellow.
Other Characteristics: Radioactive, non-fluorescent and cleavage sheets are surprisingly brittle.
Associated Minerals include bismutite, torbernite, zeunerite, uraninite and other uranium minerals.
Notable Occurences include the type locality of Weisser Hirsch Mine, Schneeberg, Saxony, Germany also at the Miracle Mine, Kern County, California, USA.
Best Field Indicators are color, crystal habit, high density, non-fluorescence, radioactivity and associations.