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Formulae:
fluocerite-(Ce): CeF3
fluocerite-(La): LaF3
Fluorides
Weakly RADIOACTIVE
Localities
The Wellington Lake pegmatite, Park county, Colorado, USA, is a
niobium-yttrium-fluorine type
pegmatite, known for its unusual rare-earth-element
enrichment, and hosted in granite. Major constituents of the
pegmatite are
quartz, perthite,
cleavelandite, iron oxides and
biotite. Accessory minerals include fluocerite,
bastnäsite, columbite,
cyrtolite and minor uranium-thorium species. Well developed tabular crystals
of fluocerite are epitaxially overgrown by bastnäsite, and occur in a matrix of irone-oxide boxwork associated
with quartz crystals. The
bastnäsite overgrowth is
zoned with respect to rare-earth elements and exhibits linear bands of enrichment in
neodymium, samarium,
gadolinium and yttrium.
The fluocerite-bastnäsite crystals
appear to be late in the paragenesis
(R&M 91-4.371-373).
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