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Formula: Cu7S4
Sulphide
Crystal System: Orthorhombic
Specific gravity: 5.68 calculated
Hardness: 3
Streak: Black
Colour: Bluish grey
Environments
Anilite occurs in hydrothermal copper ores. Associated minerals
include
bornite, chalcopyrite,
covellite and djurleite
(Mindat).
Localities
At the Mount Kelly deposit, Gunpowder District, Queensland, Australia, the deposit has been mined for oxide and
supergene
copper ores, predominantly
malachite,
azurite and chrysocolla. The
ores overlie primary zone mineralisation consisting of
quartz - dolomite -sulphide veins
hosted in dolomite-bearing
siltstone
and graphitic
schist.
Anilite is relatively common, as sooty grey grains intimately associated with
brochantite at the interface between the oxide and
supergene ore horizons
(AJM 22.1.19).
At Yarrow Creek, Yarrow Creek-Spionkop Creek deposit, Alberta, Canada, anilite is associated with
yarrowite, spionkopite,
djurleite, wittichenite,
tennantite, chalcopyrite
and bornite
(HOM).
At the Estrella Mine, Pampa Capitana, Diego de Almagro, Chañaral Province, Atacama, Chile, anilite is
associated with djurleite and
covellite
(HOM).
At the type locality, the Ani mine, Ani-machi, Kitaakita City, Akita Prefecture, Japan, anilite is found as
prismatic or platy crystals up to 5 mm in drusy parts of the quartz vein.
Most samples consist of djurleite and anilite intergrown in a
definite orientation or in an epitactic relation.
Djurleite was occasionally found as single crystals, and in some of the
specimens anilite was the dominant constituent, with a very small amount of
djurleite
(AM 54.1256-1269). Another associated mineral is covellite
(HOM).
At the Matsumine deposit, Odate, Akita, Japan, anilite occurs in a Kuroko ore deposit (HOM).
Kuroko-type deposits consist of
intimately mixed sphalerite, galena and
baryte, associated (in places) with large masses of pyrite
and gypsum. These deposits are a subtype of the volcanogenic massive sulphide ore deposits
(Mindat).
At Rassal, Loch Kishorn, North West Highlands, Scotland, UK, a variety of copper sulphide minerals,
including anilite, have been identified from a narrow vein within dolostone
(JRS 15.54).
At the Baltic Mine, Baltic, Houghton county, Michigan, USA, several samples of chalcocite-bearing
vein material carried small grains of anilite. The anilite seems to be restricted to
quartz-rich portions of thin carbonate-quartz-sulphide
veinlets, and is intimately associated with chalcocite. Additional minerals present in the
veinlets include native copper, metallic grains of
copper-arsenic alloys, and masses of
copper arsenide phases
(R&M 86-2.174).
Alteration
At room temperature, djurleite, anilite and
covellite are
stable. Above about 70oC anilite decomposes to high digenite and
covellite
(AM 55.106-117).
Natural leaching of copper sulphides results in a change from
djurleite to anilite to spionkopite to
yarrowite to covellite. Anilite specimens
leached artificially in a ferric sulphate solution show a compositional change corresponding to the change from anilite to
yarrowite but do not develop the hexagonal yarrowite
structure. These leached anilite specimens develop a structure similar to the pseudocubic structure of
geerite
(CM 19.583-591).
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