Yofortierite , Microcline (FOV 6.9 x 4.3 mm) Locality: Demix-Varennes quarry, Saint-Amable sill, Varennes & St-Amable, Lajemmerais RCM, Montérégie, Québec, Canada The width of the yofortierite tuft is about 1 cm. Found June 1996. MOB coll. The white plates are microcline. — Photo: Modris Baum · Public domain
Yofortierite
Yofortierite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₅Si₈O₂₀(OH)₂·7H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Palygorskite, Clay structural group.
Key properties: Mohs hardness 2.5; specific gravity 2.18; Silky luster; optically biaxial.
IMA symbol Yof, IMA status: approved, named in 1974.
A late-stage hydrothermal mineral in pegmatite veins within nepheline syenite in an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada);.
It is found associated with Analcime, s¶erandite, eudialyte, polylithionite, aegirine, microcline, albite (Mont Saint-Hilaire, Canada).
The name refers to Yves Oscar Fortier (1914{), former Director of the Geological Survey of Canada (1964–1972).