Compact radial sprays of white microcrystals of the extremely rare Ca-Be-phosphate mineral parafransoletite from the type and only known locality worldwide in the Tip Top mine (Tip Top Mine, Fourmile, Custer County, South Dakota, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Parafransoletite
Parafransoletite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₃Be₂(PO₄)₂(PO₃OH)₂·4H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 2.5; specific gravity 2.54; Vitreous, silky in aggregates luster; optically biaxial.
IMA symbol Pfsl, IMA status: approved, named in 1989.
A rare secondary hydrothermal mineral on fracture surfaces in beryl in a complex granite pegmatite.
It is found associated with Beryl, mitridatite, whitlockite, hurlbutite, roscherite, montgomeryite, englishite, robertsite.
Its name comes from the Greek para, for near, and its dimorphous relation to fransoletite.