Walpurgite Locality: Walpurgis Flacher vein, Weißer Hirsch Mine (Shaft 3), Neustädtel, Schneeberg District, Erzgebirge , Saxony , Germany ( Locality at mindat.org ) Size: 2.5 x 1.9 x 1.5 cm. This specimen contains crystals of bright yellow walpurgite showing extremely well-developed, sharp crystal form (distinguishing them from a later find of richer coverage, but smaller crystal size). The crystals are quite large for the species and so much coverage on one specimen is also uncommonly seen. From the style of crystallization, quantity, and size of the crystals (to 1.2 mm) this specimen is from the type find of the species in the 1870s. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Walpurgite
Walpurgite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Bi₄O₄(UO₂)(AsO₄)₂·2H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 3.5; specific gravity 6.59; Pale brownish yellow streak; Adamantine to greasy luster; optically biaxial.
IMA symbol Wpg, grandfathered status — known before the IMA’s founding, named in 1871.
A rare secondary mineral found in the oxidized zone of Bi–U–As-bearing hydrothermal mineral deposits.
It is found associated with Trögerite, zeunerite, uranosphaerite, uranospinite, torbernite (Schneeberg, Germany).
The name refers to its first-noted occurrence in the Walpurgis vein, Schneeberg, Germany.