Foshagite Locality: Crestmore quarries, Crestmore, Riverside Co., California ( Locality at mindat.org ) A really rich specimen of solid material, composed of the rare silicate foshagite in lateral crystals grown parallel to each other. Al Ordway collected this in the early 1970s, himself. I have not seen such pieces for sale in my time, of this species, and it seems to be a good one for size and richness, compared to other examples I have found through MINDAT. TYPE LOCALITY 5.8 x 4.3 x 2.7 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Foshagite
Foshagite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₄(SiO₃)₃(OH)₂.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 3; specific gravity 2.73; Silky luster; optically biaxial.
IMA symbol Fos, grandfathered status — known before the IMA’s founding, named in 1925.
Found in thin veins in thermally altered limestone (Crestmore, California, USA; Kilchoan, Scotland) or melilite skarn (Dupezeh Mountain, Iraq).
It is found associated with Hillebrandite, calcite, vesuvianite, garnet, thaumasite (Crestmore, California, USA); merwinite, larnite, kilchoanite (Kilchoan, Scotland); perovskite.
The name refers to William Frederick Foshag (1894–1956), Curator of the Smithsonian mineral collections, Washington, D.C., USA, who studied Crestmore minerals.