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Formula: Na6Mg(UO2)2(CO3)6.6H2O
Hydrated carbonate, uranyl mineral
Crystal system: Monoclinic
Specific gravity: 3.256 calculated for the empirical formula
Hardness: 2
Streak: White
Colour: Pale yellow
Luminescence: Fluoresces green under both long wave and short wave UV
Solubility: Readily soluble in water at room temperature
Environments
Sedimentary environments
Hydrothermal environments
Localities
At the type locality, the Markey Mine, Red Canyon Mining District, San Juan County, Utah, USA, leószilárdite
was found underground. The workings lie 1 km southwest of the Blue Lizard mine.
All large uranium deposits in the area of Red Canyon are characterised as
channel-type sediments from streams that deposited the Shinarump
conglomerate, and commonly cut into the underlying reddish
brown silty sandstones and
mudstones. The mine now lies abandoned and post-mining oxidation of
primary minerals in the humid underground environment is responsible for
producing interesting secondary
uranium minerals, including abundant
andersonite and
natrozippeite
Leószilárdite is a relatively rare mineral in the
secondary carbonate assemblage and is found in areas with
abundant andersonite and
gypsum, along with the other
secondary minerals
bayleyite, čejkaite,
johannite, natrozippeite
and chalcanthite coating veins of
uraninite in sulphide-laden carbonaceous wood fragments.
Leószilárdite forms as aggregates of long thin pale yellow blades individually reaching 0.2 mm long, and
pale yellow pearlescent masses to 2 mm in size composed of thin plates. Crystals are transparent with a vitreous
lustre, while crystalline masses exhibit a pearly lustre
(MM 81.5.1039-1050).
Leószilárdite from the Markey Mine -
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