Walpurgite

Formula: Bi₄(UO₂)(AsO₄)₂O₄.2H₂O

Origin of name: locality Walpurgis vein, Weisser Hirsch mine, Saxonay, Germany

Crystal system: Triclinic

Crystal class: 1

Twinning: very common on {010}

Unit cell: a = 7.13 Å, b = 10.44 Å, c = 5.49 Å, a = 101.6°, b = 110.8°, g = 88.3°

Colour: Colourless, wax-yellow to straw-yellow

Diaphaneity: Transparent to translucent

Luster: Adamantine to greasy

Habit: Crystals lath-like, elongated on c-axis, to 2 mm, in subparallel aggregates and radial groups

Hardness: 3.5

Specific gravity: 5.95

Cleavage: 1; {010} perfect

Tenacity: Brittle

Streak: Yellow white

Synonyms/varieties:

Comments: dimorphous with orthowalpurgite