Locality: Poudrette quarry (Demix quarry; Uni-Mix quarry; Desourdy quarry; Carrière Mont Saint-Hilaire), Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada FOV 1.1 x 1.3 mm. Via Monteregian Min. MOB coll. The brown color seems typical for phosinate from Kola (at least as posted on Mindat). In this case the brown is "enhanced" by the ubiquitous MSH cavity coating. Phosinate is a very rare mineral - even at MSH. But it's from Horvath so the ID should be good. — Photo: Modris Baum · CC0
Phosinaite-(Ce)
Phosinaite-(Ce) is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₁₃Ca₂Ce(SiO₃)₄(PO₄)₄.
It crystallizes in the orthorhombic crystal system (space group P22_12_1).
Key properties: Mohs hardness 3.5; specific gravity 2.62–3; Vitreous luster; optically biaxial.
IMA symbol Psi-Ce, IMA status: approved, named in 1973.
Filling interstices between large crystals of anorthoclase in alkalic pegmatites in a differentiated alkalic massif (Khibiny massif, Russia); in ussingite veinlets in a differentiated alkalic massif (Lovozero massif, Russia).
It is found associated with Anorthoclase, nepheline, aegirine, lomonosovite, lamprophyllite (Khibiny massif, Russia); belovite, nordite, neptunite, vuonnemite (Lovozero massif, Russia).
The name refers to PHOsphorus, SIlicon, and sodium, NAtrium, in the composition.