Monazite-(Sm)
Monazite-(Sm) is an exceedingly rare representative of the monazite group, with samarium being the dominant rare earth element in its structure. It is the samarium analogue of monazite-(Ce), monazite-(La), and monazite-(Nd). It is only the second known mineral with samarium being the mineral-forming element, after florencite-(Sm). The group contains simple rare earth phosphate minerals with the general formula of ATO4, where A = Ce, La, Nd, or Sm (or, rarely, Bi), and B = P or, rarely, As. The A site may also bear Ca and Th.
Intro adapted from Wikipedia (CC BY-SA).
Monazite-(Sm) is an IMA-recognized mineral species in the phosphate class, with the chemical formula Sm(PO₄).
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Monazite structural group.
Key properties: specific gravity 5.478; White streak; Vitreous to greasy luster; optically biaxial.
IMA symbol Mnz-Sm, IMA status: approved, named in 2001.
From the inner intermediate zone of a lepidolite-subtype granitic pegmatite.
It is found associated with Quartz, albite, lithian muscovite, manganocolumbite (Annie Claim); zircon, allanite, ilmenite, magnetite, hematite, fergusonite, xenotime (Shimo-ono).
The suffix designates the Sm-dominant analog of monazite-(Ce), monazite-(La), and monazite-(Nd).