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Harrisonite
Harrisonite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaFe²⁺₆(SiO₄)₂(PO₄)₂.
It crystallizes in the hexagonal crystal system (space group R-3m).
Key properties: Mohs hardness 5; specific gravity 4.02; Pale yellow streak; Vitreous luster; optically uniaxial.
IMA symbol Hrs, IMA status: approved, named in 1991.
A minor but wide-spread constituent in a layered iron silicate-quartz-apatite body in gneisses, probably a shaly and phosphatic iron formation metamorphosed to the granulite facies.
It is found associated with Fluorapatite, quartz, fayalite, ferrosilite, almandine, ilmenite, biotite, zircon, monazite-(Ce).
The mineral was named to honor Dr. James Merritt Harrison (1915–1990), former Director of the Canadian Geological Survey.