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Formula: Na4ZrSi6O16.2H2O
Unclassified silicate, zirconium-bearing mineral
Specific gravity: 2.71
Hardness: 5
Streak: White
Colour: White, pale lilac to violet
Solubility: Insoluble in 10% hydrochloric or nitric acid
Luminescence: Pale yellow fluorescence in long wave and short wave UV, bright green photoluminescence
Common impurities: Mn
Environments
Terskite occurs in pegmatite veins in
syenite; it has been found forming hollow
pseudomorphs replacing
lovozerite, and also replacing
eudialyte
(Dana).
Localities
At the Saint-Amable sill, Varennes & St-Amable, Lajemmerais RCM, Montérégie, Québec, Canada, terskite is
associated with eudialyte,
microcline, zakharovite,
aegirine, nenadkevichite,
manganoneptunite and
shkatulkalite
(HOM).
At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada,
terskite occurs in sodalite xenoliths (Dana) asociated with
villiaumite, ussingite,
gmelinite,
epistolite, eudialyte,
polylithionite and albite
(HOM).
There are two co-type localities, Alluaiv Mountain and the Yubileinaya pegmatite, Karnasurt Mountain, both in the
Lovozersky District, Murmansk Oblast, Russia. Here terskite occurs in alkalic
pegmatites assocated with
K-feldspar, hackmanite,
davyne, arfvedsonite
and aegirine
(AM 69.212).
At Alluaiv Mountain, Lovozersky District, Murmansk Oblast, Russia, terskite occurs as plates up to 3.5 mm in
size in veins in syenite
pegmatites Associated minerals include
K-feldspar, sodalite,
davyne, arfvedsonite
aegirine, and many zirconium
silicates, such as
eudialyte
(AM 69.212).
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