narsarsukite

{{infobox mineral | name = Narsarsukite | category = Silicate mineral | image = Narsarsukite-20220.jpg | imagesize = | alt = | caption = 1.3 cm crystal of narsarsukite from Mont Saint-Hilaire | formula = | IMAsymbol = Nar | molweight = | strunz = 9.DJ.05 | dana = | system = Tetragonal | class = Dipyramidal (4/m) H-M symbol: (4/m) | symmetry = I4/m | unit cell = a = 10.72, c = 7.95 [Å]; Z = 4 | color = Honey to lemon-yellow, reddish brown, brownish gray, tan, pink; may be green from inclusions; may show color zoning | colour = | habit = Occurs as flat tabular to equant, striated crystals In divergent, radiating groups; massive | twinning = | cleavage = Good on {100} and {110} | fracture = Uneven to subconchoidal | tenacity = Brittle | mohs = 5.5 - 7 | luster = Vitreous, pearly on {110} | streak = White | diaphaneity = Transparent to translucent | gravity = 2.64-2.83 | density = | polish = | opticalprop = Uniaxial (+) | refractive = nω = 1.609 nε = 1.630 | birefringence = δ = 0.021 | pleochroism = Weak; O = colorless to yellow; E = colorless to honey-yellow | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }} Narsarsukite is a rare silicate mineral with either the chemical formula or .

It was first described in 1900 for an occurrence in the Narsarsuk pegmatite in the Ilimaussaq intrusive complex of West Greenland. It has also been reported from a syenite which intruded limestone in the Sweetgrass Hills, Montana, and within hornfels and marble xenoliths in the alkalic intrusive of Mont Saint-Hilaire, Quebec. It occurs associated with aegirine, microcline, albite, elpidite, epididymite, taeniolite, pectolite, calcite, galena and quartz. thumb|left| Narsarsukite from Whitlash, Liberty County, Montana {size: 5.6 x 5.4 x 5.1 cm)