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Formula: FeCr2O4
Oxide, marokite supergroup,
paramorph of chenmingite
and chromite, chromium-bearing
mineral
Crystal System: Orthorhombic
Specific gravity: 5.63 measured, 5.342 calculated
Environments
Xieite is a high-pressure polymorph of chromite. The P-T conditions
for the phase transformation from chromite to xieite are estimated
to be 20 to 23 GPa and 1800 to 2000°C. Xieite could be a host phase for
chromium, aluminium,
iron, magnesium and
molybdenum and other metallic elements in the deep Earth
(Mindat).
Localities
At the type locality, the Suizhou meteorite, Xihe, Zengdu District, Suizhou, Hubei, China, xieite occurs in
a shock vein in the chondrite meteorite, formed by
solid-state transformation of chromite under shock-induced high pressure
and temperature. Associated minerals include ringwoodite,
majorite, lingunite,
tuite, olivine,
pyroxene and chromite
(HOM ).
The shock veins also contain other high-pressure polymorphs including
majorite-pyrope
garnet, akimotoite and
magnesiowüstite
(EJM 30.165-169).
At the Tissint Martian meteorite, Tata Cercle, Tata Province, Souss-Massa Region, Morocco,
chenmingite is a high-pressure mineral, occurring as micrometer- to
submicrometer-sized lamellae within precursor chromite grains along with
xieite and iron- and chromium- rich ulvöspinel next to
shock-induced melt pockets. Both chenmingite and xieite formed
by solid-state transformation of precursor chromite under high pressure
and high temperature during the Tissint impact event on Mars. The xieite regions are always in contact with
melt pockets, whereas chenmingite lamellae only occur within
chromite, a few micrometers away from the melt pockets. This arrangement
suggests that chenmingite formed under similar pressures as
xieite but at lower temperatures
(AM 104.10.1521–1525).
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