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Formula: (Fe,Ni)3+xS4 (x≈ 0-0.3)
Sulphide, pyrrhotite group
Crystal System: Trigonal
Specific gravity: 4.32 measured, 4.32 calculated
Hardness: 4½
Streak: Dark grey
Colour: Brownish black, bronze-yellow
Magnetism: Strongly ferromagnetic
Environments
Sedimentary environments
Hydrothermal environments
Smythite formed as a low-temperature oxidation product of strongly magnetic
pyrrhotite, as inclusions in calcite
crystals in quartz geodes, and also in hydrothermal veins. Associated
minerals include pyrite, greigite,
mackinawite, pyrrhotite,
marcasite, magnetite,
sphalerite, galena,
chalcopyrite and calcite
(HOM).
Localities
At the Bird River Mines, Lac-du-Bonnet area, Manitoba, Canada, the ore occurs along a fault zone. The samples used
consist of disseminated to massive sulphides, including pyrrhotite,
chalcopyrite, pyrite,
sphalerite, pentlandite,
smythite, marcasite and
violarite. The principal non-metallic minerals are
amphibole, quartz and
chlorite
(CM 11: 514-519).
At the Atikokan mining area, Rainy River District, Ontario, Canada, the ore occurs in lenses and irregular masses
in a highly altered gabbro. The samples examined consist of a matrix
of talc, chlorite,
amphibole and carbonates containing irregular masses of sulphides
and magnetite. The sulphide minerals include
pyrrhotite, pyrite,
chalcopyrite, pentlandite,
smythite and sphalerite
(CM 11: 514-519).
At the Nicopor mine, Pays Plat Lake Area, Thunder Bay District, Ontario, Canada, the ore occurs along the contact
between amphibolite and
granite. The samples investigated consist of disseminated sulphides
in a siliceous matrix. The principal ore minerals are pyrrhotite,
pyrite and magnetite;
chalcopyrite, smythite, and
violarite are present in small amounts.
Quartz and feldspar comprise most of
the gangue minerals, although chlorite,
amphibole and mica are also present
(CM 11: 514-519).
At the Silverfields mine, Coleman Township, Cobalt area, Cobalt-Gowganda region, Timiskaming District, Ontario, Canada,
smythite has been found closely associated with the silver-bearing veins
that contain abundant sulphides, mainly pyrite,
pyrrhotite, marcasite,
sphalerite, galena and
chalcopyrite, as well as sparse
pyrargyrite, native silver and
acanthite. The matrix consists mainly of
calcite with minor quartz and
chlorite.
The smythite occurs in two distinct assemblages. In one it is associated with
pyrite, marcasite and
sphalerite in a matrix of calcite.
In the second assemblage smythite is associated with galena,
chalcopyrite, pyrrhotite and
sphalerite in a matrix consisting mainly of
quartz with minor amounts of calcite.
It appears that the smythite was deposited directly from solution at a low temperature not far removed from
room temperature
(AM 55.1650-1658).
At the Lorraine mine, Rouyn-Noranda TE, Abitibi-Témiscamingue, Quebec, Canada, the ore is reported to occur at
the contact of andesite and
gabbro. The ore samples investigated consist chiefly of
pyrrhotite and chalcopyrite
in a matrix of quartz, chlorite,
calcite and feldspar. Other ore
minerals in the samples include smythite, pentlandite,
violarite, pyrite,
marcasite and magnetite
(CM 11: 514-519).
At the Francon quarry, Montréal, Quebec, Canada, smythite occurs very rarely as flakes and crystals less than
0.5 mm across, and rosette-like aggregates. Smythite is sometimes associated with
pyrrhotite, and also albite,
analcime, baryte,
calcite, dawsonite,
fluorite, quartz,
siderite and strontianite
(Min Rec 37-1.43).
At the type locality, State Route 37 road cut (6), Bloomington, Monroe county, Indiana, USA, smythite and
pyrrhotite occur chiefly as inclusions in
calcite crystals in quartz geodes in
limestone with thin beds of
shale and siltstone. The
geodes range commonly from 1 to 6 inches but may be more than 2 feet in diameter. At the road cut
smythite and pyrrhotite occur as inclusions in
calcite, although at other localities they have also been found imbedded in
dolomite, baryte or, rarely, in
quartz.
A generalised paragenetic sequence can be given for geodes containing smythite and
pyrrhotite. The sequence of deposition within the fractured
quartz shell is: siderite,
dolomite, and calcite of two
generations enclosing millerite, baryte,
smythite, pyrrhotite, and later
marcasite and pyrite. The included
sulphides occur in both generations of calcite. The greatest concentration
of smythite, however, is just inside the surface of the first generation of
calcite. No smythite or
pyrrhotite was found in the surrounding rock
(AM 42.309-333).
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