Anhydrous arsenate containing hydroxyl
Hardness: 3 to 4
Colour: White to gray-
Preisingerite is a rare secondary mineral in the oxidised zone of
some arsenic-bearing hydrothermal mineral deposits.
At the type locality, the San Francisco de los Andes mine, San Juan, Argentina, preisingerite is found in the weathering zone associated with rooseveltite, mixite, beudantite and bismutite. (HOM) This mine is a breccia pipe deposit, related to granodiorite plutons, with tourmaline, quartz and other minerals. The most abundant primary ore minerals are pyrite, arsenopyrite, bismuthinite, chalcopyrite, digenite and tetrahedrite. The deposit once contained a substantial weathering zone with many arsenate minerals which originated from the decomposition of arsenopyrite, scorodite, beudantite, olivenite, conichalcite, clinoclase, rooseveltite and preisingerite. (AM67.833-840)
At Cerro Negro de la Aguadita, which is a trench in the weathering zone of a deposit of the same type as San Francisco de los Andes, rooseveltite, preisingerite and mixite were found. In both deposits preisingerite usually occurs together with rooseveltite; these are the most abundant bismuth minerals in the weathering zone, while bismutite and mixite are infrequent. Preisingerite frequently forms pseudomorphs after bismuthinite, and it is occasionally found as masses impregnated by small quantities of beudantite or bismutite (AM67.833-840).
At the Clara mine, Baden-Württemberg, Germany, preisingerite is associated with bismutostibiconite, atelestite and beyerite (HOM).
At Schneeberg, Saxony, Germany, preisingerite has been found on a specimen of pucherite (AM67.833-840).
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