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Formula: Na2Co(SO4)2.4H2O
Hydrated sulphate, blödite group,
cobalt-bearing mineral
Crystal system: Monoclinic
Specific gravity: 2.29 measured, 2.347 calculated
Hardness: 2½
Streak: White
Colour: Reddish pink in aggregates
Luminescence: Not fluorescent under UV
Solubility: Dissolves slowly in water
Environments
Sedimentary environments
Hydrothermal environments
Localities
At the type locality, the Blue Lizard Mine, Red Canyon Mining District, San Juan County, Utah, USA, specimens
containing both cobaltoblödite and manganoblödite were
collected underground. The mineralised channels were found in interconnected
sandstone and
conglomerate bodies that formed in braided stream
environments. Ore minerals have been deposited as replacements of wood and other organic material and as
disseminations in enclosing sandstone.
The main ore minerals are uraninite in association with
pyrite, chalcopyrite,
bornite and covellite. After
working ceased in 1978, supergene oxidation of
primary ores in the wet underground environment of the mine
yielded different secondary minerals, mainly sulphates as
efflorescence crusts on the surfaces of mine walls.
Cobaltoblödite and manganoblödite are very rare and occur
as intimate intergrowths with Mn-Co-Ni-bearing blödite in direct
association with chalcanthite,
gypsum, johannite,
sideronatrite, quartz
and feldspar. Other minerals found in the proximity include
atacamite, baryte,
bornite, brochantite,
chalcopyrite, copiapite,
covellite, cyanotrichite,
ferrinatrite,
halotrichite,
metavoltine,
natrozippeite,
pseudojohannite, pyrite,
romerite, rhomboclase,
tamarugite, uraninite
and several uranyl sulphates.
Cobaltoblödite occurs as grains up to 200 microns in size, whereas
manganoblödite occurs as anhedral isometric grains up to 60
microns in size. Grains of
these two minerals are combined in aggregates and crusts covering areas of up to 2 x 2 cm2 on the
surface of other sulphates. In aggregates and crusts both minerals are intimately intergrown with each other and
with Mn-Co-Ni-bearing blödite. The three minerals cannot be distinguished
one from another by visual methods. Cobaltoblödite and
manganoblödite are transparent and colourless in single grains and
are reddish pink in aggregates and crusts, with a white streak and a vitreous lustre
(MM 77.3.367-383).
Cobaltoblödite from the Blue Lizard Mine -
Image
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