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Formula: (Al,Mg)Fe3+4(SO4)6(OH,O)2.20H2O
Hydrated sulphate containing hydroxyl, copiapite group
Crystal System: Triclinic
Specific gravity: 2.163 calculated
Hardness: 2 to 3
Streak: Light yellow
Colour: Pale lemon-yellow to deep yellow
Solubility: Soluble in water
Environments
Sedimentary environments
Hydrothermal environments
Fumeroles
Aluminocopiapite is a secondary mineral formed by
oxidation of pyrite in coal deposits and
shale; it may also be of fumarolic origin. It is associated with
pyrite
(HOM).
Localities
There are two co-type localities, Mosquito Fork, Forty Mile River, Southeast Fairbanks Census Area, Alaska, USA, and
Temple Mountain, San Rafael Mining District, Emery county, Utah, USA.
At Mosquito Fork, Forty Mile River, Southeast Fairbanks Census Area, Alaska, USA, aluminocopiapite occurs as a
thin local efflorescence in sheared and crushed bedrock of the river bank near an old prospect pit. The bedrock in the
area is probably schist, and appears to include fragments of
quartzite and metamorphosed
shale. The crushed rock immediately associated with the
aluminocopiapite is composed largely of quartz,
albite, chlorite,
kaolinite and lesser amounts of
muscovite and pyrite. The
aluminocopiapite occurs as minute, fragile lemon-yellow scales and as earthy blooms covering surfaces in the
sheared rocks, and appears to form locally by the oxidation of pyrite
(AM 52.1220-1223).
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