A very small yellow single crystal of the extremely rare Ca-Mg phosphate mineral stanfieldite from the type locality in the Estherville meteorite (Estherville Meteorite, Emmet County, Iowa, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Stanfieldite
Stanfieldite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₄Mg₅(PO₄)₆.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: optically biaxial.
IMA symbol Stf, IMA status: approved, named in 1966.
A rare component of some meteorites.
It is found associated with Olivine, whitlockite, farringtonite, troilite.
The mineral was named to honor Stanley Field (1875-1964), former Chairman of the Board of Trustees of the Field Museum of Natural History, Chicago, Illinois, USA.