Micheelsenite from Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada — Photo: Modris Baum · CC0
Micheelsenite
Micheelsenite is an IMA-recognized mineral species in the phosphate class, with the chemical formula (Ca,Y)₃Al(PO₃OH)(CO₃)(OH)₆·12H₂O.
It crystallizes in the hexagonal crystal system (space group P6_3). It is a member of the Ettringite structural group.
Key properties: Mohs hardness 3.5–4; specific gravity 2.15; White streak; Vitreous luster; optically uniaxial.
IMA symbol Msn, IMA status: approved, named in 1999.
A late-stage hydrothermal product in alkaline pegmatite.
It is found associated with Aegirine, albite, ancylite-(Ce), catapleiite, fluorite, microcline, monteregianite-(Y), natrolite, nenadkevichite, rhodochrosite, sérandite in pegmatites.
The mineral was named to honor Professor Emeritus of Mineralogy, Harry Ingvar Micheelsen (b. 1931) of the University of Copenhagen, Denmark. He discovered the Nanna pegmatite.