Images
Formula: Mg3O6(UO2)8(SO4)4(OH)2.28H2O
or
Mg3O6(U6+O2)8(SO4)4(OH)2.28H2O
Sulphate, uranyl mineral
Crystal System: Triclinic
Specific gravity: 4.03 measured, 3.83 calculated
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).
Marécottite from Jáchymov - Image
At the type locality, La Creusaz 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).
Marécottite from La Creusaz - Image
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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