Formula: PbFe3+3(AsO4)(AsO3OH)(OH)6 hydrated arsenate containing hydroxyl
Segnitite forms a series with beudantite
Specific gravity: >4.2
Hardness: 4
Streak: Pale yellow
Colour: Greenish to yellowish-brown

Hydrothermal environments

At the Kintore pit, New South Wales, Australia, segnitite is found in the oxidised zone of lead-zinc sulphide ore bodies where it overgrows beudantite on a matrix of goethite encrusting quartz and small spessartine crystals. It is also associated with mimetite, carminite, bayldonite, agardite-Y and mawbyite.

At Roughton Gill, Cumbria, segnitite occurs with carminite and beudantite in fractures in quartz-rich rock.

At the San Rafael Mine, Nevada, segnitite occurs as a crystalline aggregate in pods of oxidised galena and anglesite with kaolinite and covellite. In the altered rock bordering the pods segnitite occurs with scorodite, carminite and mimetite, and with adamite in pods of limonite gossan.

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