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Formula: Na2Mg(UO2)2(SO4)4.18H2O
Hydrated sulphate, uranyl mineral
Crystal system: Monoclinic
Specific gravity: 2.626 calculated for the empirical formula, 2.563 for the ideal formula
Hardness: 2
Streak: White
Colour: Pale greenish yellow
Solubility: Easily soluble in water at room temperature
Common impurities: Zn,Cu,Fe
RADIOACTIVE
Environments
Wetherillite is a relatively new mineral, approved in 2014.
Localities
At the type locality, the Blue Lizard Mine, Red Canyon Mining District, San Juan County, Utah, USA, ore minerals
(especially uraninite, and the sulphides
pyrite, chalcopyrite,
bornite and covellite) were
deposited as replacements
of wood and other organic material and as disseminations in the enclosing
sandstone. Since the mine closed in 1978, oxidation of
primary ores in the humid underground environment has
produced a variety of secondary minerals, mainly sulphates,
as efflorescent crusts on the surfaces of mine walls. The vast majority of the
secondary minerals contain essential Na, but the source of
the Na enrichment is not known.
Bobcookite and wetherillite occur together with other
secondary minerals including
boyleite, chalcanthite,
dietrichite, gypsum,
hexahydrite, johannite,
pickeringite and rozenite.
The bulk of the matrix consists of quartz crystals that are recrystallised
counterparts of the original grains of the sandstone. Other
minerals remaining from the original sandstone include
feldspar, rare almandine and
zircon. Minerals related to the ore deposition include
baryte, bornite,
chalcopyrite, covellite,
pyrite and uraninite. Other
secondary minerals in the general assemblage include
aluminocoquimbite,
atacamite, belakovskiite,
blödite, bluelizardite,
brochantite, calcite,
cobaltoblödite,
copiapite, coquimbite,
cyanotrichite,
d’ansite-(Mn), dickite,
epsomite, fermiite,
ferrinatrite, gerhardtite,
gordaite, halite,
kieserite, kröhnkite,
lishizhenite,
manganoblödite,
meisserite, metavoltine,
natrozippeite,
oppenheimerite, plasilite,
pseudojohannite,
rhomboclase, römerite,
sideronatrite and
tamarugite.
Wetherillite commonly occurs as pale greenish yellow prisms or blades with irregular terminations up to ~1 mm
long in subparallel intergrowths, divergent sprays and jackstraw aggregates. The crystals are transparent with a
vitreous lustre
(MM 79.3.695-714).
Wetherillite from the Blue Lizard Mine -
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