Monazite-(Sm) is an exceedingly rare representative of the monazite group, with

samarium Samarium is a chemical element with symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samar ...

being the dominant

rare earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

in its structure. It is the samarium analogue of

monazite-(Ce) Monazite-(Ce) is the most common representative of the monazite group. It is the cerium-dominant analogue of monazite-(La) Monazite-(La) is a relatively rare representative of the monazite group, with lanthanum being the dominant rare earth elemen ...

monazite-(La) Monazite-(La) is a relatively rare representative of the monazite group, with lanthanum being the dominant rare earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the ...

, and

monazite-(Nd) Monazite-(Nd) is a relatively rare representative of the monazite group, with neodymium being the dominant rare earth element in its structure. This variety of monazite is typically colored bright rose-red. It is the neodymium analogue of monazite- ...

. 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 A''T''O₄, 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. Mindat, Monazite Group, https://www.mindat.org/min-29313.html

References

{{reflist Samarium minerals Phosphate minerals Monoclinic minerals Minerals in space group 11 Minerals described in 2002