Images
Formula: FeCrP
Phosphide of iron and chromium,
florenskyite group
Crystal system: Orthorhombic
Colour: Creamy white
Environments
Metamorphic environments
Meteorites
Localities
At the Hatrurim Basin, Tamar Regional Council, Beersheba Subdistrict, Southern District, Israel, iron phosphides
with significant variations of Cr (up to 18 wt%) and V (up to 8.6 wt%) contents were detected in
gehlenite-bearing
breccia. Investigations of the Fe2P phosphides showed that
when the V+Cr content is higher than 0.26 apfu (atoms per formula unit), a transition from the hexagonal
barringerite to orthorhombic
allabogdanite takes place;
allabogdanite is a high-pressure (greater than 8 GPa)
paramorph of
barringerite.
Pseudowollastonite associated with Cr-V-bearing
allabogdanite is an indicator of phosphide crystallisation at high
temperature (greater than 1200°C) and low pressure. Thus, at the low pressure close to ambient, when more than
13at% (atomic percentage) Fe in Fe2P is substituted by Cr and V, the orthorhombic
paramorph is stable. The orthorhombic phosphide with the highest Cr
and V contents belongs to the andreyivanovite species. This is the first finding on Earth of that very rare
mineral first described from the Kaidun meteorite
AM 108.8.1506-1515)
The Kaidun meteorite, Hadhramaut Governorate, Yemen, the type locality of andreyivanovite, fell in 1980. It
is a unique breccia containing an unprecedented variety of fragments
of different chondritic as well as
achondritic lithologies. Andreyivanovite was found
as individual grains and linear arrays of grains with a maximum dimension of 8 µm within two masses of Fe-rich
serpentine. In one sample, it is associated with Fe-Ni-Cr sulphides and
florenskyite. Andreyivanovite is creamy white in reflected
light, with a metallic lustre. It could have formed as a result of cooling and crystallisation of a melted precursor
consisting mainly of Fe-Ni metal enriched in P, Ti, and Cr. Serpentine
associated with andreyivanovite would then have formed during aqueous alteration on the parent asteroid
(AM 93.8.1295-1299).
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