Formula: NaCe2(CO3)2[F2x(CO3)1-x]F
Anhydrous carbonate containing halogen, cerium-bearing mineral
Crystal System: Hexagonal
Specific gravity: 4.126 calculated
Hardness: 3 to 3½
Colour: Beige, beige-yellow, light lemon yellow to pinkish
Luminescence: Not fluorescent under UV
Solubility: Dissolves slowly with effervescence in room temperature, dilute hydrochloric acid

Hydrothermal environments


There are two co-type localities, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada and the Aris quarries, Aris, Windhoek Rural, Khomas Region, Namibia.

At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada (one of the type localities), arisite-(Ce) has been discovered in small alkaline pegmatite veins and in lenticular patches within sodalite syenite and sodalite syenite xenoliths. It occurs as pale pink to silvery to very pale brown, micaceous plates with a rough hexagonal outline, or as thin, narrow strips that grade to thin fibres. It also develops as isolated crystals, in rosettes, irregular clusters and in spherical aggregates 0.1 to 2 mm in diameter. Individual plates are exceedingly thin, no more than 5 mm in thickness, and all crystals have a distinctive pearly lustre.
Within the alkaline pegmatites, it is associated with aegirine, albite, a clinoamphibole, a eudialyte-group mineral, microcline, mosandrite, natrolite, gonnardite and fluorapatite.
Within the sodalite syenite xenoliths, arisite-(Ce) is associated with aegirine, “tetranatrolite”, polylithionite, fluorite, sodalite, serandite, microcline, catapleiite, pyrite, pyrochlore, pyrrhotite, goethite, an alkali feldspar and an astrophyllite-group mineral.
Arisite-(Ce) is a rare, late-stage accessory mineral found predominantly in cavities (5–15 mm across) in alkaline pegmatite veins in the nepheline syenite, and, more rarely, in sodalite syenite xenoliths.
It is noteworthy that arisite-(Ce) in the sodalite syenite xenoliths is the only phase not covered by a brown to pale brown film (probably a hydrocarbon), indicating that it is paragenetically one of the last minerals to crystallise (CM 48.661-671).

At the Demix-Varennes quarry, Saint-Amable sill, Varennes & St-Amable, Lajemmerais RCM, Montérégie, Quebec, Canada, arisite-(Ce) occurs as thin, flexible, pearly, silvery white, rounded to irregular micaceous plates 0.3 to 0.5 mm in diameter. The plates form spherical or rosette-like aggregates. It is associated with natrolite, aegirine, albite, manganoneptunite, rhodochrosite, sphalerite, astrophyllite and a beige to brown unidentified mineral (CM 48.661-671).

At the Aris quarries, Aris, Windhoek Rural, Khomas Region, Namibia (one of the type localities), arisite-(Ce) occurs as euhedral, hexagonal plates up to 1.5 mm across and as rare tabular, hexagonal prisms, in miarolitic cavities. The crystals are vitreous, transparent, and range in colour from beige, beige-yellow, light lemon yellow to pinkish. Associated minerals include aegirine, analcime, apatite, fluorite, manganoneptunite, microcline, natrolite, sphalerite, tuperssuatsiaite and the unnamed Fe-analogue of zakharovite.
Arisite-(Ce) is a late-stage mineral in miarolitic cavities in phonolite, a result of crystallisation from residual magmatic or hydrothermal fluids. It may be replaced by fine-grained, yellowish bastnäsite-(Ce), resulting in opaque, dull crystals (CM 48.661-671).

Back to Minerals