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Formula: (Ce,Ca)5(SiO4)3F
Nesosilicate (insular SiO4 groups), britholite group,
apatite supergroup
Specific gravity: 4.66 measured, 4.66 calculated
Hardness: 5
Streak: Pale brown
Colour: Pale yellow, tan, reddish-brown
Environments
Plutonic igneous environments
Pegmatites
Localities
At the type locality, the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec,
Canada, fluorbritholite-(Ce) occurs in vugs in
nepheline syenite,
marble xenoliths, sodalite
syenite xenoliths and
pegmatite dykes,
associated with zircon, ussingite,
steenstrupine-(Ce), sodalite,
serandite, microcline,
lueshite, lovozerite,
götzenite, fluorite,
eudialyte, chabazite, carbonate-rich
fluorapatite, calcite,
biotite, ancylite,
analcime, albite and
aegirine
(Mindat).
At the Longs Peak - St Vrain batholith near Jamestown, Jamestown District, Boulder county,
Colorado, USA, centimetre to decimetre sized mineralised pods and veins consist of zoned
mineral assemblages dominated by fluorbritholite-(Ce)
in a core 10 cm thick, with monazite-(Ce),
fluorite and minor quartz,
uraninite and sulphides. The core is surrounded by a
typically millimetre thick rim of allanite-(Ce), with
minor monazite-(Ce) in the inner part of the rim.
Bastnäsite-(Ce),
törnebohmite-(Ce) and
cerite-(CeCa) appear in an intermediate zone between core and
rim, often just a few hundreds of microns wide
(R&M 96.3.252-253).
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