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Formula: Ca10(Si2O7)3Cl2
Sorosilicate (Si2O7 groups)
Crystal system: Orthorhombic
Specific gravity: 2.93 measured, 2.931 calculated
Hardness: 3 to 4
Streak: White
Colour: White
Environments
Volcanic igneous environmenta
Metamorphic environments
Localities
At the NW slope, Shadil-Khokh volcano, Kel’ volcanic area, Greater Caucasus Mountain Range, South Ossetia, Georgia,
rusinovite was found in pyrometamorphic rock in an altered carbonate-silicate xenolith, about 2 m across,
within dacite lava. This xenolith is composed of minerals characteristic of
sanidinite facies metamorphism, such as
spurrite, larnite,
gehlenite, merwinite,
bredigite, rondorfite
and srebrodolskite. Rusinovite occurs as relatively large elongated crystals,
100 to 200 microns in length, with a characteristic macroscopic brown-orange colour, in small veins, up to 0.5 cm
wide, encountered at the exocontact zone (on the dacite side of the
contact) of the xenolith. Rusinovite was found also at the endocontact zone (on the xenolith side of the
contact) of strongly altered dacite.
The presence of microzonation at both endocontact and exocontact zones is reflected in the distribution of minerals
with different Ca:Si ratios.
At the endocontact (xenolith side of the contact), there are four zonation zones; the numbering is according to the
Ca:Si ratio increasing.
The first zone is dacite, consisting of
enstatite, albite phenocrysts
and quartz enclosed in the fine-grained aggregate of
diopside, plagioclase and
Na–K feldspar. Visible zonation of
enstatite is caused by variations of minor Fe substitutions in
composition. Ilmenite occurs as an accessory mineral.
The second zone is composed of massive gehlenite.
The third zone is comprised mostly of rusinovite and gehlenite;
hydroxylellestadite and
wollastonite are noted rarely.
The fourth zone is represented by strongly altered rock, mainly composed of
secondary Ca–Si hydrosilicates, rusinovite,
cuspidine and rondorfite.
Another type of zonation is observed at the dacite-xenolith boundary
(exocontact, dacite side).
In the first zone the altered dacite is composed of
diopside, enstatite,
plagioclase phenocrysts and
quartz. the matrix is a fine-grained aggregate of
plagioclase; ilmenite,
titanite, apatite and
pyrite occur as accessory minerals.
In the second zone towards the xenolith, wollastonite and
andradite are the main minerals, and the accessory phases include
cuspidine, gehlenite and
wadalite.
In the third zone, rusinovite occurs as a major component together with
cuspidine. Wollastonite is
present, but not as commonly as in the previous zone. Cl-bearing
hydroxylellestadite,
gehlenite,
magnesioferrite and
rondorfite are also noted.
The fourth and last zone is a strongly altered xenolith part composed mostly of
secondary Ca-hydrosilicates with the relics of
rondorfite, larnite,
cuspidine and merwinite
(Minerals 8.9.399).
At the Bellerberg volcano (Caspar quarry), Vordereifel, Mayen-Koblenz, Rhineland-Palatinate, Germany,
rusinovite was found in
pyrometamorphic rock. In the active Caspar quarry, within leucite
tephrite, small Ca-rich xenoliths
can be found, formed at high temperatures and low pressure. The main part of the xenolith is composed of
larnite, gehlenite,
rondorfite, Cl-bearing
hydroxylellestadite,
spurrite and
secondary Ca-hydrosilicates.
Perovskite, hematite,
cuspidine, a
kerimasite-like
garnet, andradite and
pyrite with chalcopyrite
intergrowths also occur here.
In addition to these minerals, the lighter part of the rock also contains rusinovite,
wollastonite, chalcopyrite,
baghdadite and lakargiite.
Aggregates of rusinovite can reach up to 200 microns in size. They contain a lot of inclusions of minerals
including gehlenite, chlorine-bearing
ellestadite, perovskite and
hematite, mainly, and strongly hydrated zones
(Minerals 8.9.399).
At the type locality, Xenolith no. 3, Lakargi Mountain, Upper Chegem volcanic caldera, Chegemsky District,
Kabardino-Balkaria, Russia, rusinovite was found in the altered carbonate-silicate xenolith within
ignimbrites. The xenolith no. 3 is also the type locality of
calcio-olivine, megawite and
toturite. Rusinovite was detected within a thin endocontact zone
(on the xenolith side of the boundary) of skarn which replaced
ignimbrite. Rusinovite forms fibres intergrown to spherulites
displaying in thin section bright interference colours. Detailed investigation of
skarn zonation revealed a rusinovite zone, composed of fine
needles and fibrous aggregates of rusinovite, often with inclusions of numerous
wadalite grains. Relics of earlier, high temperature,
skarn minerals, such as larnite,
rondorfite, rankinite,
pavlovskyite, cuspidine,
tazheranite, baddeleyite,
garnet minerals of the
kerimasite - kimzeyite -
toturite series, lakargiite,
perovskite and
magnesioferrite are found.
Low-temperature alteration is evidenced by hillebrandite,
afwillite, tobermorite,
grossular-katoite,
hydrocalumite and
ettringite group minerals.
Trabzonite and jennite
crystallised after rusinovite and wadalite is replaced by
grossular-katoite. In
several cases, fibrous pseudomorphs of rusinovite after
wollastonite have been found
(EJM 23.837-844).
Rusinovite from the Lakargi Mountain -
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