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Formula: Na3Fe2+(PO4)(CO3)
Anhydrous carbonate with phosphate
Crystal System: Monoclinic
Specific gravity: 2.95 to 3.16 measured, 2.95 calculated
Hardness: 4
Streak: White
Colour: Colourless, with rose, yellowish, or greenish tint
Environments
Pegmatites
Metamorphic environments
Bonshtedtite occurs in veinlets associated with alkai-carbonate metasomatism of alkalic massifs
(Webmin).
Associated minerals include shortite,
thermonatrite, eitelite,
neighborite, trona,
burbankite, barentsite,
siderite and aegirine
(HOM).
Localities
At Koashva Mt, Khibiny Massif, Murmansk Oblast, Russia, megakalsilite
was found in a large body of hyperagpaitic pegmatite in
ijolite – urtite, near
their contact with apatite –
nepheline rocks. The
pegmatite consists of an intensely mineralised core composed
mainly of water-soluble villiaumite,
natrite, thermonatrite and
natrophosphate, and a silicate rim consisting of very
large aegirine spherulites up to 1.5 m across. Other minerals occurring
mostly in the central zone of the body and at its contact with the
aegirine-dominant rim are
pectolite, microcline,
sodalite and lomonosovite;
less common phases are chkalovite,
vitusite, and rare earth element- and
strontium- enriched
fluorapatite, with sporadic
cancrinite, natrolite, alkali
amphibole, phlogopite,
lamprophyllite, lovozerite,
umbite, belovite,
fluorcaphite, nacaphite,
nefedovite, bonshtedtite,
sphalerite, galena and
molybdenite
(CM 40,961-970).
There are two co-type localities, the Vuonnemiok River Valley, Khibiny Massif, Murmansk Oblast, Russia, and the
Kovdor Massif, Murmansk Oblast, Russia.
At the Vuonnemiok River Valley, Khibiny Massif, Murmansk Oblast, Russia, bonshtedtite occurs as fine-grained
aggregates in shortite and as crystals up to 0.5 x 2 x 5 mm3.
In drill cores it is associated with shortite,
thermonatrite, eitelite,
trona, neighborite and other
minerals
(AM 68.1038).
At the Kovdor Massif, Murmansk Oblast, Russia, most hydrous phosphates in the complex occur as freestanding crystals
and clusters on water-clear crystals of late dolomite that coat fissures
and vugs in dolomite veins and adjacent rocks. There is intensive
dissolution and replacement of tabular crystals and aggregates of
pyrrhotite, and of granular aggregates of
fluorapatite, by late iron-rich
minerals.
The wide variety of minerals replacing primary
pyrrhotite attests to extensive hydrothermal leaching in an open system.
The variability of conditions was due to repeated influx of solutions and their interaction with the fractured rocks.
Change of composition of hydrothermal solutions due to this interaction is clearly shown by the presence of
bonshtedtite and nastrophite in vugs in
dolomite veins enclosed by
nepheline pyroxenite
(CM 38.1477-1485)
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