Balkanite

balkanite

djurleite

stromeyerite

wittichenite

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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

Hydrothermal 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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