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Formula: Na2(Ti,Fe3+)Si4(O,F)11
Inosilicate (chain silicate)
Crystal System: Tetragonal
Specific gravity: 2.64 to 2.83 measured, 2.81 calculated
Hardness: 7
Streak: White
Colour: Yellow, yellowish-white, greyish-white, honey-yellow, tan, greenish-yellow
Environments
Plutonic igneous environments
Pegmatites
Metamorphic environments
Localities
At the Papanduva pluton, Morro Redondo complex, Tijucas do Sul, Paraná, Brazil, narsarsukite has been found
in the peralkaline granite. Two distinct narsarsukite
generations, one late magmatic and the other post-magmatic, were identified. The magmatic generation consists of
larger, euhedral to subhedral variably zoned crystals and late poikilitic (where large later-formed crystals
surround smaller early-formed crystals of other minerals) intergrowths between narsarsukite and
albite laths, representing the crystallisation of the latest melt pockets.
The post-magmatic generation forms smaller, typically fibrous crystals and irregular aggregates that occur
interstitially or replace the primary
mafic minerals, particularly
arfvedsonite. The magmatic generation is enriched in Zr and depleted
in Al. The Fe3+ and Al contents show a positive correlation for the magmatic crystals, but a negative
correlation for the post-magmatic narsarsukite. The Al/Fe3+ ratios are higher in the post-magmatic
crystals
(MM 87, 896-907).
At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, narsarsukite occurs in
hornfels, igneous breccia and
marble xenoliths in an intrusive alkaline
gabbro-syenite complex
(HOM).
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At the type locality, the Narssârssuk pegmatite, Narsaarsuk Plateau, Igaliku, Kujalleq, Greenland, narsarsukite occurs in pegmatite
associated with aegirine, microcline,
albite, elpidite,
epididymite, tainiolite and
quartz
(HOM).
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At Sage Creek, Sweet Grass Hills, Liberty county, Montana, USA, narsarsukite occurs in
quartz veins cutting an orthoclase -
albite - aegirine -
quartz hybrid rock in a zone adjacent to a syenite
stock intruding limestone. Pectolite is the
dominant vein mineral, and quartz and narsarsukite are also abundant;
calcite and galena are the remaining
primary minerals in the veins. The paragenetic sequence appears to be
pectolite and narsarsukite oldest, followed by
galena and calcite, with
quartz youngest of all. Minerals associated with narsarsukite include
aegirine, pectolite,
calcite, feldspar,
galena, manganese-bearing pectolite and
quartz (AM 44.265-273, HOM). Fresh material was found at the old prospect pit on one of
the veins, associated with galena, alunite,
epidote, clinozoisite,
apatite and feldspar
(AM 20.598-601).
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