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Formula: Ca3Sn2(SiAl2)O12
Nesosilicate (insular SiO4 groups), schorlomite group,
garnet supergroup, tin-bearing
mineral
Crystal system: Isometric
Specific gravity: 4.3 calculated
Streak: Ashy yellow
Colour: Pale brown to yellow
Environments
Volcanic igneous environments
Metamorphic environments
Irinarassite is a relatively new mineral, approved in 2011 and to date (June 2025) confirmed only from the
type locality, although there is one other doubtful locality.
Localities
At the type locality, Xenolith no. 7, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District,
Kabardino-Balkaria, Russia, the sanidinite facies
xenolith comprises a chegemite central zone and
larnite-cuspidine marginal zone.
Irinarassite is found in the complex mixture of minerals forming
pseudomorphs after zircon
ranging up to 200 microns in size. These pseudomorphs occur at the
immediate contact of skarn with unaltered
ignimbrite. The contact rock is represented by a thin
endoskarn zone. Larnite,
cuspidine, rondorfite,
As-bearing fluorellestadite and
hydroxylellestadite are the main minerals of this zone.
Fluorite, rankinite and
wollastonite are minor minerals and
secondary minerals are
katoite-grossular,
ettringite, hillebrandite,
bultfonteinite and unidentified Ca-hydrosilicates. As a rule,
accessory minerals are represented by newly formed magnesioferrite,
srebrodolskite, Th-bearing
perovskite, lakargiite and
relics of ignimbrite minerals such as
fluorapatite, titanium-bearing
magnetite, thorianite and
zircon. The pseudomorphs after
zircon in which irinarassite was discovered commonly preserve the form
of the original zircon.
Garnet of the
kerimasite–kimzeyite series,
lakargiite and tazheranite
are the main minerals in the pseudomorphs.
Lakargiite and tazheranite
are concentrated in the central zones of the pseudomorphs, and
minerals of the schorlomite group develop on the periphery of the
pseudomorphs or along radial cracks.
Baddeleyite, baghdadite,
magnesioferrite and zircon
relics are relatively rare constituents of the pseudomorphs.
Irinarassite forms zones and irregular spots typically less than 10 microns in size in
kerimasite–kimzeyite series
minerals. In rare instances, irinarassite occurs as crystals 2 to 3 microns in size
(MM 77.6.2857-2866).
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