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Formula: CuI
Normal halide, chlorargyrite group, forms a series with
miersite
Crystal System: Isometric
Specific gravity: 5.68 measured, 5.71 calculated
Hardness: 2½
Streak: yellow
Colour: Colourless to pale yellow when fresh, turns pink to dark brownish-red
Environments
Marshite is found with oxidised copper minerals
(Webmin)
At the type locality, Broken Hill Proprietary Mine, Yancowinna county, New South Wales, Australia, marshite is
a rare halide in the oxidised zone of a metamorphosed lead,
zinc and
silver deposit, associated with
copper,
cuprite, cerussite,
malachite and
iron-manganese oxides
(HOM, Mindat)'
Microprobe analysis of marshite and miersite from Broken Hill
demonstrate extensive solid solution between the end-members, indicating the possibility of a complete solid-solution
series. Crystallisation of either miersite or
iodargyrite at Broken Hill appears to be dependent upon the local
availability and ratio of copper,
silver and iodine ions
(MM 62.4.471–475).
At Chuquicamata, Chile, marshite occurs in the oxidised zone of a
porphyry copper deposit,
associated with
atacamite, copper,
tenorite and gypsum. The
marshite, with
atacamite, lines fractures in the
sericitised and kaolinised
granodiorite. In this section of the mine,
antlerite, otherwise the principal oxidised
copper mineral at Chuquicamata,
is not stable.
The marshite crystals penetrate the atacamite and perch upon it.
(AM 24.629-635, HOM).
At Loytosuo, Finland, marshite has been found in tills over a copper
anomaly, introduced by brackish seawater
(HOM).
At the Rubtsovskoe copper, zinc and
lead deposit, Rudnyi Altai, Altai Krai, Russia, marshite has been found as
a partial pseudomorph
of an azurite nodule
(FM OP2577).
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