fluorbritholite-(Ce): (Ce,Ca)5(SiO4)3F
fluorbritholite-(Y): (Y,Ca)5(SiO4)3F
Nesosilicates (insular SiO4 groups), britholite group
Specific gravity: fluorbritholite-(Ce) 4.66; fluorbritholite-(Y) 4.609 calculated
Hardness: fluorbritholite-(Ce) 5; fluorbritholite-(Y) 5½
Streak: fluorbritholite-(Ce) Pale brown; fluorbritholite-(Y) Pale brownish to almost white.
Colour: fluorbritholite-(Ce) Pale yellow, tan, reddish-brown; fluorbritholite-(Y) Light pinkish-brown to brownish-pink; light brown; dark brown

Plutonic igneous environments


The Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada is the type locality for fluorbritholite-(Ce). It 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).

There are three Co-Type Localities for fluorbritholite-(Y), Kråkmo, Hamarøy, Nordland, Norway, Lagmannsvik, Hamarøy, Nordland, Norway and Vyuntspakhk Mt, Western Keivy Massif, Keivy Mountains, Lovozersky District, Murmansk Oblast, Russia.

At Lagmannsvik and Kråkmo, Hamarøy, Nordland, Norway, fluorbritholite-(Y) occurs in alkaline granite related pegmatites (Mindat).

At Kråkmo, Hamarøy, Nordland, Norway, fluorbritholite-(Y) is associated with fluorapatite, quartz, fluorite and allanite-(Ce) (HOM).

At Lagmannsvik, Hamarøy, Nordland, Norway, fluorbritholite-(Y) occurs in pegmatite cutting alkaline granite as irregular grains and crystals up to 1 mm embedded in granular aggregates of of cream coloured yttrium-bearing fluorite and allanite-(Ce). Associated minerals include yttrium-bearing fluorite, allanite-(Ce), quartz, magnetite, fluorapatite, aluminocerite-(Ce), bastnäsite-(Ce), britholite-(Y), gadolinite-(Y), hundholmenite-(Y), thalénite-(Y), kainosite-(Y) and tengerite-(Y) (HOM, Mindat).

At Vyuntspakhk Mt, Western Keivy Massif, Keivy Mountains, Murmansk Oblast, Russia, fluorbritholite-(Y) occurs in a microcline variety amazonite-bearing pegmatite vein (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-(Ce) 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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