Beudantite

Formula: PbFe3+3(AsO4)(SO4)(OH)6 compound arsenate
Beudantite Group > Alunite Supergroup
Specific gravity: 4.48
Hardness: 3½ to 4½
Streak: Black to grey
Colour: Dark green, brown, black
Solubility: Soluble in HCl.
Environments

Hydrothermal environments

Beudantite is a secondary mineral occurring in the oxidised zones of polymetallic deposits. Some beudantite may contain minor antimony Sb replacing iron Fe.

Localities

Germany

At the Clara Mine, in the Black Forest, beudantite is common, lining cavities in baryte or quartz, and associated with segnitite, kintoreite, corkite and dussertite.

United Kingdom

At Burdell Gill, Cumbria, beudantite is uncommon, but it sometimes occurs on baryte or quartz associated with mimetite and carminite.

At Roughton Gill, Cumbria, beudantite occurs as crusts on quartz, and also in cellular quartz veinstone, with baryte and lepidocrocite. It is sometimes associated with carminite.

At Sandbed, Cumbria, beudantitee occurs as a encrustation on mimetite with scorodite and pharmacosiderite. A mineral intermediate between beudantite and segnitite occurs in cavities in quartz, apparantly formed by the oxidation of primary arsenopyrite.

At Short Grain, Cumbria, beudantite occurs on quartz or baryte associated with mimetite, arseniosiderite and carminite. It sometimes forms pseudomorphs after mimetite. Other associates include supergene baryte and bariopharmacosiderite.

At Silver Gill, Cumbria, beudantite occurs coating mimetite crystals.

USA

At the San Rafael Mine, Nevada, beudantite occurs in boxwork limonite associated with segnitite, mimetite and adamite, and also within quartz-lined vugs.

Common impurities: Al,P