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Formula: Cu4Fe5S8
Sulphide, talnakhite group
Crystal system: Orthorhombic
Specific gravity: 4.33 calculated
Hardness: 4½
Streak: Black
Colour: Brass-yellow
Common impurities: Ni
Environments
Localities
At the type locality, Mooihoek Farm 255 KT, Fetakgomo Tubatse Local Municipality, Sekhukhune District Municipality,
Limpopo, South Africa, the deposit, which was mined for platinum in the
1920's and 1930's, is a pipe-shaped hortonolite -
dunite
pegmatite.
Mooihoekite and haycockite were found in small massive sulphide
samples from the sulphide-poor hortonolite -
dunite. In polished sections,
mooihoekite occurs in areas up to 1 mm2 and as an
intergrowth with haycockite. Haycockite occurs up to about 500 microns in size. The larger areas of
mooihoekite commonly show fractures filled with veinlets of
magnetite, about 1 micron wide. Other irregular fractures are filled
with gangue or with a
valleriite-type mineral.
Troilite always occurs with a
copper-rich rim; other minerals are a
copper-bearing pentlandite,
mackinawite, sphalerite
stars and moncheite. Haycockite shows polysynthetic twinning that
occasionally appears in polished section
(AM 57.689-708).
At the Birch Lake Deposit, Ely-Hoyt Lakes Area, St. Louis County, Minnesota, USA, haycockite is associated
with mooihoekite, copper,
troilite, pentlandite,
cubanite and magnetite
(HOM).
Haycockite from Minnesota - Image
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