Fluocerite: Properties and Occurrences

Fluocerite is a mineral, a cerium, lanthanum fluoride, formula (Ce, La)F3. It is a mineral consisting of a reddish yellow fluoride of cerium and related metals. It is recognized as two different minerals depending on the cation, fluocerite-(Ce) and fluocerite-(La), corresponding respectively to lanthanum trifluoride and cerium trifluoride. Both crystallize in the trigonal system.

Fluocerite-(Ce) was first described (without the Ce) in 1845 from hydrothermal veins in granite in Sweden. Fluocerite-(La) was first described in 1969 from the type locality in central Kazakhstan.

General information

  • Formula: (La, Ce)F3
  • Hardness: 4 – 5
  • Crystal System: Trigonal
  • Name: In allusion to its relationship to Fluocerite-(Ce), plus the “-(La)” suffix due to the dominance of lanthanum in the composition.

Fig: Fluocerite-(Ce)

Properties

  • Luster: Vitreous, Resinous, Pearly
  • Transparency: Transparent, Translucent
  • Color: Light yellow; darkening to yellow- and red-brown; colorless to pale pink (transmitted light)
  • Streak: Off-white
  • Tenacity: Brittle
  • Fracture: Irregular/Uneven, Splintery, Sub-Conchoidal
  • Density: 5.93 – 6.14 g/cm3 (Measured)

Occurrence: In hydrothermal quartz veins in granite.

Association: Quartz.

Distribution: From the Zhanuzak area, Kent massif, Karaganda region, central Kazakhstan.

 

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