Elpidite

phyllosilicate

labuntsovite

Formula: Na2ZrSi6O15.3H2O
Phyllosilicate (sheet silicate)
Specific gravity: 2.52 to 2.62
Hardness: 5
Streak: White
Colour: Colorless, white, gray, yellowish, orange, brown, beige
Solubility: Decomposes only in HF (Dana)
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 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).

Common impurities: Ti,Nb,Ca,K,F,Cl

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