Thorbastnäsite , Albite (FOV 1.3 mm x 1.9 mm) 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 Description: Thanks to Marc F. Analyzed find. Stereo pair (not very clear in mono). MOB coll. It has been claimed that this is really röntgenite with thorbastnäsite but the analysis label (see child photo) only mentions the latter. (And there are those who claim that röntgenite is a bit like cold fusion. Beyond my ken ...) The tiny black things look like pseudo-octahedral brookite (similar to Dana 3rd ed. fig. 726). But too small to be sure. — Photo: Modris Baum · Public domain
Thorbastnäsite
Thorbastnäsite is an IMA-recognized mineral species in the carbonate class, with the chemical formula ThCa(CO₃)₂F₂·3H₂O.
It crystallizes in the hexagonal crystal system (space group P-62c). It is a member of the Bastnäsite structural group.
Key properties: specific gravity 4.04.
IMA symbol Tbsn, IMA status: approved, named in 1965.
Found in metasomatic albitite and quartz–muscovite veinlets in an alkaline exocontact surrounding a syenite intrusive.
It is found associated with Rinkite, zircon, pyrochlore, euxenite-(Y), thorite.
The name refers to a thorium-bearing mineral chemically similar to bastnäsite.