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Formula: Pd25Ge9
Germanide, palladium-bearing
mineral
Crystal System: Trigonal
Specific gravity: 10.933 calculated
Colour: White, pinkish brown
Environments
Marathonite and palladogermanide were the first two
germanide minerals to be discovered and approved, in 2016, in association
at the common type locality.
Localities
At the type locality, the Marathon deposit, Coldwell complex, Thunder Bay District, Ontario, Canada, marathonite occurs as rounded, elongated grains up to 33 × 48 μm. Associated minerals include
vysotskite, a
gold-silver alloy,
isoferroplatinum,
germanium-bearing
keithconnite, majakite,
coldwellite,
cuprorhodsite-ferhodsite,
kotulskite and mertieite,
the base-metal sulphides, chalcopyrite,
bornite, millerite and
a rhodium-bearing pentlandite,
oberthürite and
torryweiserite, and silicates including a
clinoamphibole and an iron-rich chlorite-group mineral.
The observed paragenetic sequence is:
bornite → marathonite →
palladogermanide.
Marathonite is stable over the range of 550–970 °C observed in an assemblage of
clinoamphibole, an iron-rich
chlorite-group mineral and fragmented
chalcopyrite, considered to have developed at temperatures of
500–600°C
(CM 59.1865-1886).
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