Fluocerite

fluocerite

bastnasite

cerium

tornebohmite

Images

Formulae:
fluocerite-(Ce) CeF3
fluocerite-(La) LaF3
Normal halides
Specific gravity: fluocerite-(Ce) 6.13, fluocerite-(La) 5.93
Hardness: fluocerite-(Ce) ½ to 5, fluocerite-(La) 4 to 5
Streak: fluocerite-(Ce) Yellow-white, fluocerite-(La) White
Colour: fluocerite-(Ce) Light yellow; darkening to yellow- and red-brown; colourless to pale pink in transmitted light, fluocerite-(La) Greenish yellow
Solubility: Fluocerite-(Ce) is soluble in sulphuric acid, insoluble in hydrochloric or nitric acid
Weakly RADIOACTIVE both
Environments

Plutonic igneous environments
Hydrothermal environments

Fluocerite-(Ce) occurs in granitic rocks. Fluocerite-(La) occurs in hydrothermal quartz veins in granite (Webmin, HOM).

Localities

There are two co-type localities for fluocerite-(Ce), Broddbo and Finnbo, both at Falun, Dalarna County, Sweden.

At the Bastnäs Mines, Riddarhyttan, Skinnskatteberg, Västmanland County, Sweden, fluocerite-(Ce) is one of the rarest cerium minerals. It is found as grains in törnebohmite - bearing cerite-(Ce), and is replaced by bastnäsite along cleavage cracks in the fluocerite (MinRec 35.3.196).

At its type locality, Zhanuzak, Kent Massif, Karkaraly, Karaganda Region, Kazakhstan, fluocerite-(La) occurs in hydrothermal quartz veins in granite (Dana, AM 69.577).

Near Odegi, Nasarawa, Nigeria, fluocerite-(Ce) occurs in albite pegmatites (Dana).

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, microcline-feldspar variety perthite, albite variety cleavelandite, iron oxides and biotite. Accessory minerals include fluocerite, bastnäsite, columbite, zircon variety 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 niodymium, samarium, gadolinite and yttrium. The fluocerite-bastnäsite crystals appear to be late in the paragenesis (R&M 91-4.371-373).

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