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Formula: Ni3Ge
Germanide of nickel,
auricupride subgroup,
non-stoichiometric perovskites group,
perovskite supergroup
Crystal system: Isometric
Specific gravity: 8.927 calculated
Hardness: 5½
Streak: Silver
Luminescence: No fluorescence under UV
Solubility: Insoluble in 10% hydrochloric acid
Magnetism: Non-magnetic
Environments
Volcanic igneous environments
Meteorites
Localities
The type locality is the Olgafrankite type locality, Dzheltul'skii massif, Kureika river, Taymyrsky Dolgano-Nenetsky
District, Krasnoyarsk Krai, Russia.
Germanium is a trace element that rarely forms its own minerals but plays
a significant role in geochemical and cosmochemical classification schemes. The geochemical behaviour of
germanium is very variable, depending on the redox environment and
sulphur activity in the geosystems. Siderophile (having an affinity for iron)
germanium, in the form of native
germanides, has been reported in several terrestrial and
meteoritic
occurrences, but the majority of these phases have been poorly characterised.
Olgafrankite, previously mentioned in the Rumuruti meteorite, has been discovered in terrestrial
basalts of the Dzhaltul intrusion. Crystals up to 5 × 7 μm in size were found within
magnetite-pentlandite
assemblages confined to massive centimetre-sized aggregates of native iron.
Other associated minerals are graphite,
cohenite, germanium-bearing
taenite, tetrataenite and
various sulphides. In reflected light, olgafrankite is bright white with a pink tint.
Olgafrankite can be an important germanium carrier in some reduced
assemblages, in particular in iron and stony-iron
meteorites, where the significant correlations between
nickel and germanium may be
accounted for by the presence of finely dispersed olgafrankite precipitates
(AM 110.10.1640–1648).
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