Fluocerite

Fluocerite, also known as tysonite, is a mineral consisting of cerium and lanthanum fluorides, with the chemical formula (Ce,La)F3.[1][2] The end members are classified as two different mineral types depending on the cation, fluocerite-(Ce) and fluocerite-(La), corresponding respectively to lanthanum trifluoride and cerium trifluoride. Both crystallize in the trigonal system.[3]

Fluocerite-(La)
General
CategoryMineral
Formula
(repeating unit)		(La,Ce)F3
Strunz classification03.AC.15 (03)
Dana classification09.03.04.02 (09)
Crystal systemTrigonal
Crystal classHexagonal scalenohedral
Space groupP3c1 (No. 165)
Unit cell328.80 ų (Calculated from Unit Cell)
Identification
Formula mass196.02
ColourGreenish-yellow
Crystal habitPlaty, tabular
CleavageIndistinct, Imperfect
Mohs scale hardness4-5
LusterVitreous
StreakWhite
DiaphaneityTransparent to translucent
Density5.93
Birefringence0.006
Fluocerite-(Ce)
General
CategoryMineral
Formula
(repeating unit)		(La,Ce)F3
Strunz classification3/A.10-20
Dana classification9.3.4.1
Crystal systemTrigonal
Crystal classHexagonal Scalenohedral
Unit cell320.86 ų (Calculated from Unit Cell)
Identification
Formula mass196.99
ColourLight yellow; darkening to yellow- and red-brown; colourless to pale pink (transmitted light)
Crystal habitMassive, Primsatic
CleavageDistinct/Good
FractureIrregular/Uneven, Splintery, Sub-Conchoidal
TenacityBrittle
Mohs scale hardness4.5-5
LusterVitreous, Resinous, Pearly
StreakYellow-white
DiaphaneityTransparent to translucent
Specific gravity5.93 - 6.14
Density5.93 - 6.14 g/cm3 (Measured)
Birefringence0.005 - 0.007

Fluocerite-(Ce) was first described (without the Ce) in 1845 from hydrothermal veins in granite in Sweden.[4] Fluocerite-(La) was first described in 1969 from the type locality in central Kazakhstan.[3] The name tysonite was given in 1880 to the same type of mineral found in Colorado.[5][6] Tysonite-type structure is used for rare-earth fluorides with the P3c1 space group structure.[7]

References
  1. "Fluocerite-(La) Mineral Data". webmineral.com. Retrieved 2021-02-12.
  2. "Fluocerite-(Ce) Mineral Data". webmineral.com. Retrieved 2021-02-12.
  3. "Fluocerite-(La)". www.mindat.org. Retrieved 2021-02-12.
  4. "Fluocerite-(Ce)". www.mindat.org. Retrieved 2021-02-12.
  5. Geijer, Per (1921-01-01). "On Fluocerite and Tysonite". Geologiska Föreningen i Stockholm Förhandlingar. 43 (1–2): 19–23. doi:10.1080/11035892109443886. ISSN 0016-786X.
  6. Allen, Oscar D., and W. J. Comstock. "Bastnaesite and tysonite from Colorado." American Journal of Science 3.113 (1880): 390-393.
  7. Dudney, Nancy J.; West, William C.; Nanda, Jagjit (2015-07-09). Handbook Of Solid State Batteries (Second ed.). World Scientific. ISBN 978-981-4651-91-2.
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