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Formula: Na2ZrSi6O15.3H2O
Phyllosilicate (sheet silicate), zirconium-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 2.52 to 2.62 measured, 2.59 calculated
Hardness: 5
Streak: White
Colour: Colourless, white, grey, yellowish, orange, brown, beige
Solubility: Decomposes only in HF (Dana)
Common impurities: Ti,Nb,Ca,K,F,Cl
Environments
Plutonic igneous environments
Pegmatites
Elpdite occurs in alkaline granites,
aplite
dykes and pegmatites, and also in
nepheline syenites and their
pegmatites. It sometimes forms as a
pseudomorph after
eudialyte and calcite,
and may form epitactic intergrowths with labuntsovite (Dana).
At Mont Saint-Hilaire, Montérégie, Quebec, Canada, elpidite has been found in silicate veins and vugs in the
nepheline syenite (AM 58.106-109).
Pseudomorphs of elpidite after
serandite have also been found here (Dana ).
At the Francon quarry, Montréal, Québec, Canada, elpidite is relatively rare. it occurs on
analcime
crystals with cryolite, and it is also associated with
weloganite, analcime,
calcite, albite,
marcasite, synchysite-(Ce) and
brookite (MinRec 37.1.32).
The type locality is the Narsaarsuk pegmatite, Narsaq, Kujalleq, Greenland, Denmark.
At Tarbagatai, eastern Kazakhstan, elpidite occurs in aegirine -
quartz-feldspar
pegmatites (Dana).
At the Lovozero Massif, Murmansk Oblast, Russia, elpidite occurs in
albitised
nepheline syenite and associated
pegmatites,
aegirine-rich granite, and
fenites, associated with albite,
quartz, aegirine,
epididymite and labuntsovite
(HOM).
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