Images
Formula: ZnCr2O4
Oxide of zinc and chromium,
spinel subgroup,
oxyspinel group,
spinel supergroup
Crystal System: Isometric
Specific gravity: 5.434 calculated
Hardness: 5½ to 6
Streak: Brown
Colour: Brown, brownish grey in reflected light
Magnetism: Weakly paramagnetic
Environments
Placers
Metamorphic environments
Localities
At the type locality, the Srednyaya Padma mine, Zaonezhie peninsula, Medvezhyegorsky District, Republic of Karelia,
Russia, zincochromite forms tiny brownish black euhedra, generally 2 to l0 microns across, rarely to 50 microns,
with quartz and amorphous chromium -
vanadium - iron oxides and hydroxides,
formed from the breakdown of chromium-rich
aegirine, in micaceous metasomatites.
Translucent in thin slivers, brown streak, semimetallic lustre, cleavage absent, weakly paramagnetic
(AM 73.931-932).
Zincochromite from the Srednyaya Padma Mine -
Image
At the Quebrada Grande placers, Quebrada Grande River, Guaniamo, Bolívar, Venezuela, zincochromite associated
with chromite and
magnesiochromite was found in heavy-mineral concentrates. It occurs
in subhedral to anhedral grains from 0.1 to 0.7 mm in size. Zincochromite grains are markedly zoned, with the
rim and microfissures enriched in zinc. The
chromite crystals partly replaced by
zincochromite indicate high-temperature metasomatic processes involving
a zinc- and manganese- bearing fluid
phase
(CM 48.361-374).
Back to Minerals