Marécottite

marecottite

uraninite

magnesiozippeite

rabejacite

Images

Formula: Mg3O6(UO2)8(SO4)4(OH)2.28H2O
Sulphate
Specific gravity: 4.03
Hardness: 3
Streak: Colourless
Colour: Yellow-orange
RADIOACTIVE
Environments

Sedimentary environments
Hydrothermal environments

Sulphate-rich acid waters produced by oxidation of sulphide minerals enhance uranium mobility around uranium ores and uranium-bearing radioactive waste. Upon evaporation, several secondary uranyl minerals, including many uranyl sulphates such as marécottite precipitate from these waters (AM 88.676-685).

Localities

At the Musonoi Mine, Kolwezi, Kolwezi mining district, Lualaba, DR Congo, marécottite is a rare alteration product of selenium-bearing digenite in the oxidation zone of a uranium-bearing copper-cobalt hydrothermal ore deposit. Associated minerals include digenite, demesmaekerite, denningite and guilleminite (HOM).

At Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic, magnesiozippeite and marécottite co-exist, sometimes in the same sample (AM 88.676-685).

At the type locality, La Creusa U prospect, La Creusaz, Les Marécottes, Salvan, Saint-Maurice, Valais, Switzerland, marécottite occurs as diamond shaped platelets to 500 µm in length grouped into rosettes in hydrothermal breccia veins. It is an alteration product of uraninite and associated with uraninite, gypsum, rabejacite, johannite and some other uranium species, such as magnesiozippeite (Minrec 35.4.358, AM 88.676-685).

At the Lucky Strike No. 2 Mine, San Rafael Mining District, Emery county, Utah, USA, magnesiozippeite and marécottite co-exist, sometimes in the same sample (AM 88.676-685).

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