Phyllosilicate (sheet silicate)
Specific gravity: 3.05 to 3.09
Hardness: 6 to 6½
Colour: Colourless, lemon yellow, brown, pale blue
Solubility: Insoluble in acids
Common impurities: Al,Fe,Nb,Mn,Mg,Ca,Sr,K
At Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, leucosphenite occurs in pegmatite in syenite associated with albite, aegirine, narsarsukite, molybdenite, calcite and fluorite (HOM, AM 57.1801-1822).
The type locality is the Narssârssuk pegmatite, Narsaarsuk Plateau, Igaliku, Kujalleq, Greenland, Denmark, leucosphenite occurs in pegmatite in syenite associated with elpidite, aegirine, epididymite, albite and polylithionite (HOM, AM 57.1801-1822).
At the Alaiski massif, Turkestan, Kazakhstan, leucosphenite is found with reedmergnerite, eudialyte, stillwellite, pyrochlore, calcite and galena as accessories in pegmatites composed mainly of microcline, aegirine, albite and quartz (AM 57.1801-1822).
At the Karnasurt mountain, Lovozersky district, Murmansk Oblast, Russia, leucosphenite occurs with neptunite and eudialyte (FM 75755).
At the Inaglina massif, Yakutia, Russia, leucosphenite occurs in pegmatite in syenite in aegirine - feldspar veins associated with arfvedsonite, eudialyte, neptunite, lamprophyllite and lorenzenite (HOM, AM 57.1801-1822).
At the Green River Formation, Utah and Wyoming, USA, leucosphenite occurs with shortite and analcime (Dana) as an authigenic mineral in shale (HOM). Nepheline has not been found here, although hydrous sodium aluminosilicates such as analcime are abuirdant and widespread (AM 57.1801-1822).
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