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Formula: Ag5Cu9HgS8
Sulphide, silver- and mercury-
bearing mineral
Crystal System: Monoclinic
Specific gravity: 6.318 measured on synthetic material, 6.421 calculated
Hardness: 3½
Colour: Steel-grey
Environments
Balkanite occurs in association with bornite,
chalcocite, chalcopyrite,
djurleite, digenite,
tennantite, stromeyerite,
mckinstryite,
wittichenite, bismuth,
rammelsbergite,
native amalgam,
cinnabar, pyrite,
calcite, baryte and
aragonite
(HOM).
Localities
At the type locality, the Sedmochislenitsi Mine, Balkan Mts, Vratsa Province, Bulgaria, the stratiform deposit
results from the hydrothermal metasomatism developed around a system of tectonic faults cutting
limestone and
dolostone. Two types of industrial ores are mined in the deposit,
lead-zinc ores in the upper levels and
copper ores at greater depths. Two clear-cut mineral associations are
observed:
(a) A tennantite -
chalcopyrite association, characteristic of the middle levels of
the deposit. Tennantite and
chalcopyrite are the main ore minerals, and
galena, sphalerite,
tetrahedrite and silver-rich
freibergite are present in smaller amounts along with
pyrite and marcasite.
A sequence of silver minerals, mainly sulphosalts, is paragenetically
connected with this association; these minerals are pyrargyrite,
pyrostilpnite,
stephanite, polybasite,
pearceite, acanthite,
jalpaite and minor amounts of
native silver.
(b) A tennantite - bornite
association, wherein the main ore minerals are tennantite,
bornite, chalcopyrite and
primary
chalcocite, is characteristic of the lowest levels. It is
accompanied by another well defined silver mineral association:
stromeyerite,
mckinstryite and comparatively large amounts of
native silver which is usually
mercury-bearing. No silver
sulphosalts are found in the tennantite -
bornite association.
Balkanite is a rare mineral in the deposit and occurs only in the
tennantite - bornite
association. The associated minerals are tennantite,
bornite, chalcocite,
native amalgam,
chalcopyrite, cinnabar,
stromeyerite,
mckinstryite,
wittichenite, native bismuth,
rammelsbergite, djurleite,
digenite, pyrite,
calcite, baryte and
aragonite.
Balkanite occurs as grains up to 3 mm in size, in or around small fissures and rock cavities. Rod-like
prismatic balkanite crystals from 0.01 to 0.2 mm, striated parallel to their length, were found in cavities
overlying baryte, chalcocite,
bornite and native amalgam,
and covered by calcite and
aragonite.
Balkanite is a result of low-temperature hydrothermal activity. Together with
chalcocite, djurleite,
digenite, stromeyerite,
wittichenite, silver and
native amalgam, it is one of the last-formed minerals of the deposit.
Balkanite and chalcocite very frequently replace
tennantite and bornite
(AM 58.11-15).
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