Fransoletite Locality: Tip Top Mine (Tip Top pegmatite), Fourmile , Custer District, Custer County, South Dakota , USA ( Locality at mindat.org ) Picture width 3 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Fransoletite
Fransoletite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₃Be₂(PO₄)₂(PO₃OH)₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: Mohs hardness 3; specific gravity 2.56; White streak; Subvitreous luster; optically biaxial.
IMA symbol Fsl, IMA status: approved, named in 1982.
Formed by late-stage hydrothermal alteration of beryl and other phosphates in a zoned granite pegmatite.
It is found associated with Beryl, tiptopite, whitlockite, carbonate-apatite, montgomeryite, hurlbutite, englishite, roscherite, quartz.
The mineral was named to honor Dr. André-Mathieu Fransolet (1947-), Professor of Mineralogy, University of Liège, Liège, Belgium, for his work with primary phosphate minerals.