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Formula: Ag8SnS6
Sulphide, argyrodite group, forms a series with
argyrodite, silver- and
tin- bearing mineral
Crystal System: Orthorhombic
Specific gravity: 6.2 to 6.3 measured, 6.311 calculated
Hardness: 2½
Streak: Greyish black
Colour: Steel gray with reddish tint
Common impurities: May contain some Ge replacing Sn, and some Te or Se replacing S
Environments
Metamorphic environments
Hydrothermal environments
Canfieldite occurs in polymetallic veins, formed very late in the paragenetic sequence. Associated minerals
include argyrodite, pyrargyrite,
stephanite, acanthite,
polybasite, freibergite,
stannite, stannoidite,
cassiterite, arsenopyrite,
jordanite, marcasite,
pyrrhotite, sphalerite and
galena
(HOM).
Canfieldite is a minor ore of tin and
silver.
Localities
At the type locality, Colquechaca, Chayanta Province, Potosí, Bolivia, canfieldite crystals, to 1 cm in size,
are associated with stephanite,
stannoidite, stannite,
sphalerite, pyrrhotite,
pyrargyrite, polybasite,
marcasite, jordanite,
galena, freibergite,
cassiterite, arsenopyrite,
argyrodite and acanthite
(Mindat).
At the Revelstoke Mining Division, British Columbia, Canada, there is a
lead-zinc-silver
ore deposit at a prospect 19 miles northeast of Revelstoke. The ore consists chiefly of
sphalerite, pyrite and
galena with lesser, but appreciable, amounts of
stannite, with the remainder of the minerals, including
cassiterite, pyrrhotite,
rutile, scheelite,
silver-bearing tetrahedrite,
chalcopyrite, covellite and
cerussite occurring in very small to trace, amounts. The
tellurium-bearing canfieldite occurs as small inclusions (10-50 microns)
in galena and often at the contact between the
galena and pyrite
(CM 10.895-898).
At the Shuangjianzishan Ag-polymetallic deposit, Bairin Left Banner, Chifeng City, Inner Mongolia, China, exceptional
selenium enrichment in canfieldite (up to 11.6 wt.% of Se) has been
discovered. Canfieldite has been identified as one of the dominant
silver-bearing ore minerals in the deposit, which occurs mostly in
slate-hosted vein type
silver-lead-zinc
ore bodies. Selenium is either homogeneously or, remarkably, heterogeneously
distributed in the different canfieldite fragments studied. Chemical variations of
selenium are mostly attributable to a series of retrograde reactions
resulting in diverse decomposition and exsolution of primary
phases during cooling, or alternatively, related to influxes of selenium-rich
fluids during the formation of canfieldite
(MM 83.3.419–426).
At the Lengenbach Quarry, Fäld, Binn, Goms, Valais, Switzerland, tellurium-rich
canfieldite is hosted in a tennantite matrix. The mineral assemblage
also includes seligmannite,
thalcusite, wurtzite,
jordanite and galena.
The Lengenbach lead, thallium,
silver, arsenic,
antimony, mercury and
barium mineralisation, hosted in
dolomitic marbles, is
characterised by appreciable geochemical enrichment in lead,
thallium, arsenic and
sulphur.
Tellurium-rich canfieldite represents the first
tellurium-bearing mineral described so far (2012) at the Lengenbach quarry
(CM 50.111-118).
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