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Formula: Cu8AgBi13S24
Sulphosalt, cuprobismutite homologous series group,
bismuth-bearing mineral
Crystal System: Monoclinic
Specific gravity: 6.36 measured, 6.24 calculated
Colour: Dark bluish grey
Luminescence:
Solubility: Soluble in nitric acid; also soluble in hydrochloric acid, with precipitation of silver chloride
(Mindat)
Environments
Pegmatites
Hydrothermal environments
Cuprobismutite is a rare mineral, of hydrothermal origin with other sulphides and sulphosalts. Associated minerals include
emplectite, aikinite,
wittichenite, benjaminite,
berryite, cupropavonite,
paderaite, hodrušite,
wolframite and bismuthinite
(HOM).
Localities
At the Szklarska Poręba Huta granite quarry, Szklarska Poręba, Karkonosze County, Lower Silesian Voivodeship, Poland, small bodies
of granitic pegmatite are
common within coarsely crystalline granite. In addition to minerals typical of
granitic pegmatites, they
contain magnetite, ilmenite,
hematite, titanite,
zircon, xenotime,
monazite, thorite,
thorogummite, yttrialite,
davidite, beryl,
gadolinite-(Y), gadolinite-(Ce),
hingganite-(Y), epidote,
allanite, pumpellyite-(Mg),
pumpellyite-(Fe), clinochlore,
chamosite, laumontite,
chabazite, stilbite,
ferberite and hübnerite,
scheelite, cassiterite,
molybdenite, base-metal sulphides,
emplectite, nuffieldite,
native bismuth, some supergene
minerals, and an assemblage of newly recognised bismuth sulphosalts.
The granite itself, as well as walls of the cavities, are in some cases mineralised
with wolframite, scheelite and sulphides,
mainly pyrite, chalcopyrite and
molybdenite; the same minerals are found along with
bismuthinite and native bismuth in thin
quartz veinlets cutting the granite.
Emplectite and other bismuth sulphides, such
as aikinite, friedrichite,
krupkaite, gladite and
pekoite (all in the
aikinite-bismuthinite series),
kupčikite, hodrušite and
cuprobismutite (all in the
cuprobismutite homologous series group),
galenobismutite, cannizzarite,
cosalite, ikunolite,
joséite-A, as well as bismite,
bismutite, powellite,
koechlinite (?) and russellite as
supergene phases, are less frequent in the assemblage. However, the
cuprobismutite homologues are directly associated only with krupkaite ±
gladite ± pekoite +
bismuthinite ± chalcopyrite ±
native bismuth, and occasionally with ikunolite
and joséite-A.
It is believed that cuprobismutinite exists in the Szklarska Poręba sulphide assemblage only as nanometre-scale intergrowths
with hodrušite
(CM 50.313-324).
The Rozália Mine, Hodruša-Hámre mines, Hodruša-Hámre, Žarnovica District, Banská Bystrica Region, Slovakia,
is hosted within propylitised
andesite and quartz
diorite porphyry. The vein filling
includes galena, sphalerite and
chalcopyrite. The gangue minerals are mainly
quartz (amethyst), with lesser amounts of carbonates,
rhodonite, hematite and
baryte. Bismuth minerals,
bornite and scheelite, as well as
hematite, are typical of the deeper part of the vein.
Hodrušite, emplectite and
wittichenite, together with hematite and
chalcopyrite are the most common; in smaller amounts,
copper - lead -
bismuth sulphosalts of the
aikinite-bismuthinite series,
galena–matildite and a
cuprobismutite-like mineral occur, as well as silver minerals
(polybasite and silver-bearing
tetrahedrite).
Sulphosalts of the cuprobismutite homologous series group
are common at the Rozália mine. They usually form anhedral grains or platy laths from 10 microns up to 1 mm in size, commonly in
association with other bismuth sulphosalts, as well as with
chalcopyrite and hematite. They are usually
replaced by emplectite. Hodrušite is the
most common, whereas cuprobismutite and kupčíkite are rare.
Cuprobismutite occurs as sparsely distributed small grains intergrown with
hodrušite, emplectite,
pavonite homologues and members of the
aikinite-bismuthinite series
(CM 50.2.325–340).
At the Ni-Bi-As occurrence, Čierna Lehota, Bánovce nad Bebravou District, Trenčín Region, Slovakia, sulphosalts from the
cuprobismutite homologous series group,
hodrušite and cuprobismutite, have been found, together with associated
aikinite and bismuth-rich
tennantite
(EJM 17.1.155–162).
At the type locality, the Missouri Mine, Hall Valley, Montezuma Mining District, Park County, Colorado, USA,
cuprobismutite occurs in quartz veins as small slender crystals, generally bronzed
by oxidation and deeply striated. Occasionally the crystals are joined together laterally, forming thin corrugated plates.
Associated Minerals include wolframite group minerals,
quartz and chalcopyrite
(Mindat).
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