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Formula: NaAl(UO2)2(SO4)4.18H2O
Hydrated sulphate, uranyl mineral
Crystal System: Triclinic
Specific gravity: 2.669 calculated
Hardness: 2½
Streak: Very pale yellowish green
Colour: Lime-green to greenish yellow
Luminescence: Fluoresces bright greenish white under UV
Solubility: Moderately hygroscopic, easily soluble in water at ambient temperature
Environments
Bobcookite 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, bobcookite,
together with wetherillite, was found as a
secondary alteration phase in association with
boyleite, chalcanthite,
dietrichite, gypsum,
hexahydrite, johannite,
pickeringite and rozenite.
Bobcookite formed lime-green to greenish yellow massive veins and transparent vitreous, columnar crystals
(MM 79.695-714).
It occurred as efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of
primary minerals, such as
uraninite, pyrite,
chalcopyrite, bornite and
covellite, in a relatively humid underground environment
(HOM).
At the Markey Mine, Red Canyon Mining District, San Juan County, Utah, USA,
markeyite occurs as a
secondary phase on asphaltum (bitumen) in association with
calcite, gypsum and
natrozippeite. Other
secondary minerals in the general assemblage include
bobcookite
(MM 82.1089-1100).
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