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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
Environments
Pegmatites
Hydrothermal environments
Localities
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).
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