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Formula:
(Na,☐)2Ca(Ti,Mg,Nb)4[Si2O7]2O2(OH,O)2(H2O)4
Sorosilicate (Si2O7 groups), murmanite group,
seidozerite supergroup,
titanium- and niobium-
bearing mineral
Crystal System: Triclinic
Specific gravity: 2.70 measured, 2.85 calculated for the empirical formula
Hardness: 2½ to 3
Streak: White
Colour: Pale brownish, purple
Luminescence: Not fluorescent under UV or an electron beam
Common impurities: Mg,Mn,Fe,Nb,Al
Environments
Pegmatites
Hydrothermal environments
Calciomurmanite is a relatively new mineral, approved in 2015. It is formed by late-stage, low-temperature
hydrothermal alteration (hydration and natural cation exchange) of a high-temperature, anhydrous phosphate-bearing
titanosilicate, most likely lomonosovite and/or
paralomonosovite, in peralkaline rocks
(HOM ).
Localities
There are two co-type localities, Eveslogchorr Mt, Khibiny Massif, Murmansk Oblast, Russia, and Selsurt Mountain,
Lovozersky District, Murmansk Oblast, Russia
At Eveslogchorr Mt, Khibiny Massif, Murmansk Oblast, Russia, in the cotype specimen, a 2 × 3.5 cm fan-shaped
aggregate of calciomurmanite lamellae occurs in a hydrothermally altered peralkaline
pegmatite together with
microcline, aegirine,
lamprophyllite,
tsepinite-Ca and
tsepinite-K
(EJM 28.4.835-845).
At Koashva Mt, Khibiny Massif, Murmansk Oblast, Russia, calciomurmanite occurs in the outer zone of the
pegmatite as lamellae up to 0.5 cm in size forming chaotic
and fan-shaped aggregates. The lamellae contain relics of yellow
paralomonosovite and are associated with
aegirine, microcline,
lamprophyllite and
pectolite
(EJM 28.4.835-845).
At Selsurt Mountain, Lovozersky District, Murmansk Oblast, Russia, in the holotype,
calciomurmanite occurs as irregular lamellae up to
0.1 × 0.4 × 0.6 cm3 in size, sometimes combined in aggregates up to 3 cm in size embedded in a rock
mainly consisting of dark green acicular aegirine and
white microcline and containing
lorenzenite, fluorapatite and minor
calcite. The lamellae are most likely
pseudomorphs after crystals of an unspecified
seidozerite supergroup titanosilicate, probably
lomonosovite
(EJM 28.4.835-845).
Calciomurmanite from Selsurt Mountain -
Image
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