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Formula: Cu6(Cu4Zn2)As4Se13
Selenide,
giraudite subgroup,
tetrahedrite group,
arsenic-bearing mineral
Crystal system: Isometric
Specific gravity: 5.75 calculated
Hardness: 3½ to 4
Colour: Pale grey, with a creamy tint in reflected light
Common impurities: Hg,Fe
Environments
Plutonic igneous environments
Hydrothermal environments
Giraudite-(Zn) is a rare late-stage mineral with other selenides and
sulphides in uranium deposits
(HOM).
Localities
At the type locality, the Chaméane Uranium Deposit, Le Vernet-Chaméane, Issoire, Puy-de-Dôme, Auvergne-Rhône-Alpes,
France, three new (in 1982) selenides occur,
chaméanite, geffroyite and
giraudite-(Zn). They occur in a complex quartzitic vein
cutting granite. Three stages of mineralisation, separated by
tectonic movements causing brecciation, are recognised.
In the first stage pitchblende was deposited with copious
baryte
gangue.
In the second stage quartz occurred with
löllingite, arsenopyrite,
pyrite, chalcopyrite,
tetrahedrite, tennantite
and clausthalite, with partial replacements of
baryte by quartz,
pitchblende by chalcopyrite,
and chalcopyrite by
clausthalite.
In the third stage the selenides
bukovite, athabascaite,
umangite, eucairite,
eskebornite, more
clausthalite, together with
chaméanite, geffroyite and
giraudite-(Zn), occur with an ankerite
gangue, followed by a second generation of
chalcopyrite. Giraudite-(Zn) sometimes occurs alone and may
reach 400 microns in size
AM 67.1074-1075).
Giraudite-(Zn) from the Chaméane Uranium Deposit
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At Alberoda, Aue-Bad Schlema, Erzgebirgskreis, Saxony, Germany, among the minerals of the
selenide assemblage at the uranium
deposit, members of the giraudite-(Zn)–hakite-(Hg) solid solution
intergrown with berzelianite and
galena have been identified. They form complexly zoned, anhedral, minute
(<350 micron) grains embedded in a dolomite matrix
(CM 40.4.1161-1170).
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