Bonshtedtite

bonshtedtite

shortite

thermonatrite

eitelite

Images

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 ijoliteurtite, near their contact with apatitenepheline 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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