Monazite-(La) is a relatively rare representative of the

monazite Monazite is a primarily reddish-brown phosphate mineral that contains rare-earth elements. Due to variability in composition, monazite is considered a group of minerals. The most common species of the group is monazite-(Ce), that is, the cerium- ...

group, with

lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...

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. As such, it is the lanthanum 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-(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- ...

, and

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) Monazite-(Nd) is a rela ...

. It is also the phosphorus analogue of gasparite-(La). 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 Lanthanum minerals Phosphate minerals Monoclinic minerals Minerals in space group 14