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Formula: Na2Si2O5
Phyllosilicate (sheet silicate)
Crystal System: Monoclinic
Specific gravity: 2.48 measured, 2.51 calculated
Streak: White
Colour: Colourless
Solubility: Water soluble. Soluble in weak acids.
Common impurities: K,H2O
Environments
Natrosilite occurs in pegmatites in
nepheline syenite in differentiated alkalic massifs, associated
with microcline, analcime,
natrolite, lomonosovite,
ussingite and vuonnemite
(Dana).
Localities
At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, natrosilite
occurs in sodalite xenoliths associated with an intrusive alkalic
gabbro syenite complex
associated with revdite
HOM.
At the Khibiny Massif, Murmansk Oblast, Russia, natrosilite is associated with
aenigmatite, aegirine,
sodalite, cancrinite and
eudialyte
HOM.
At the type locality, Karnasurt Mountain, Lovozersky District, Murmansk Oblast, Russia, natrosilite occurs as
pseudohexagonal thick, tabular crystals up to 6 X 6 X 4 cm in size, intergrown with
microcline, analcime,
natrolite, lomonosovite,
ussingite and vuonnemite in
pegmatitic segregations of
nepheline syenite
(AM 61.339-340).
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