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Formula: Cu13VAs3S16
Sulphosalt, germanite group, forms a series with
sulvanite, vanadium-bearing mineral
Crystal System: Isometric
Specific gravity: 4.2 to 4.5 measured, 4.63 calculated
Hardness: 3 to 4
Streak: Black
Colour: Bronze, pinkish bronze
Common impurities: Zn,Fe,Te
Environments
Colusite is widespread in small amounts with other sulphides and sulphosalts, typically in hydrothermal veins and
disseminated copper deposits. Associated minerals include
pyrite,
tetrahedrite–tennantite,
enargite, luzonite,
stannoidite, goldfieldite,
germanite, renierite,
bornite, chalcocite,
covellite, chalcopyrite,
sphalerite and galena
(HOM).
Localities
There are two co-type localities, the Lebedinoe Au Deposi, Aldan, Sakha Republic, Russia, and the East Colusa mine,
Butte Mining District, Silver Bow County, Montana, USA.
At the Waterloo deposit, Charters Towers Region, Queensland, Australia,
bornite-bearing ores of the volcanic rock massive sulphide deposit host
germanium-bearing colusite. Associated minerals include
pyrite, chalcopyrite,
sphalerite, tennantite and
bornite. It is suggested that the colusite-group minerals formed under
moderately oxidised conditions in the ore-forming hydrothermal fluids
(CM 43.655-669).
Lorano Quarry, Torano quarrying basin, Carrara, Massa-Carrara Province, Tuscany, Italy.
Numerous quarries of the well known Carrarra marble can be found in the
surroundings of Carrara, but colusite was found only in the Lorano quarry, as small crystals up to 1 mm in size.
The snow-white matrix of marble makes a considerable contrast for
epitactic overgrowths of the colusite on sphalerite or on
wurtzite, forming beautiful specimens. The colusite crystals are
bronze-brown with a metallic lustre. Two small crystals were found in vugs in
marble. One was found associated with
quartz, albite,
fluorite and dolomite, and the second
from a different vug was found associated with quartz,
dolomite and sulvanite
(CM 19.423-427).
At the Geis Mine, Cone Butte Sub-District, Warm Springs District, Fergus county, Montana, USA, the epithermal
deposit consists of gold-silver
telluride
veins that occur along the contact between alkaline intrusive rocks (quartz
monzonite, syenite and
tinguaite porphyries) and
sedimentary rocks (shale,
sandstone, conglomerate,
limestone and dolostone).
Four stages of mineralisation have been identified; colusite occurs in the third, which is dominated by
quartz,
gold-silver
tellurides and
roscoelite. It is suggested that stage 3 mineralisation formed between
185 and 237oC. Anhedral colusite up to 1.5 mm in size is intergrown with
chalcopyrite, tetrahedrite,
pyrite, hessite,
enargite, and chalcocite
(AM 79.750-762).
At the East Colusa Mine, Butte Mining District, Silver Bow County, Montana, USA, colusite is associated with
pyrite, tetrahedrite,
bornite, chalcocite and
quartz. The colusite is found almost entirely within an area of intensely
altered quartz-monzonite.
The sequence of deposition was as follows:
(1) pyrite and early quartz
(2) colusite
(3) enargite
(4) tennantite-tetrahedrite
(5) chalcocite and bornite
(6) late quartz
Evidently the precipitation of pyrite had ceased before the
chalcocite-bornite solutions arrived
since no chalcopyrite is observed. Had
copper been present while iron and
sulphur were forming pyrite it no doubt
would have entered into the reaction in the form of chalcopyrite
(AM 18.528-533, AM 24.369-376).
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