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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. [3] The most common species of the group is monazite-(Ce), that is, the cerium-dominant member of the group. [4] It occurs usually in small isolated crystals.
It is the cerium-dominant analogue of monazite-(La), monazite-(Nd), and monazite-(Sm). It is also the phosphorus analogue of gasparite-(Ce). [ 3 ] The group contains simple rare earth phosphate minerals with the general formula of AXO 4 , where A = Ce, La, Nd, or Sm (or, rarely, Bi), and X = P or, rarely, As.
Monazite is a waxy mineral that is formed through the crystallization of igneous rocks and the metamorphism of clastic sedimentary rocks. [25] This mineral is typically mined in placer deposits, with gold commonly found as a byproduct. [25] The rare earth element neodymium is found in monazite, making it a rare mineral. [25]
This variety of monazite is typically colored bright rose-red. It is the neodymium analogue of monazite-(Ce) , monazite-(La) , and monazite-(Sm) . [ 4 ] The group contains simple rare earth phosphate minerals with the general formula of A T O 4 , where A = Ce, La, Nd, or Sm (or, rarely, Bi), and B = P or, rarely, As.
Since mineral assemblages at equilibrium are dependent on pressures and temperatures, by measuring the composition of the coexisting minerals, together with using suitable activity models, the P-T conditions experienced by the rock can be determined. [1] After one equilibrium constant is found, a line would be plotted on the P-T diagram. [20]
Monazite-(La) is a relatively rare representative of the monazite group, with lanthanum being the dominant rare earth element in its structure. As such, it is the lanthanum analogue of monazite-(Ce) , monazite-(Nd) , 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). It is only the second known mineral with samarium being the mineral-forming element, after florencite-(Sm). [3]
The composition of the lanthanides was about 49% cerium, 33% lanthanum, 12% neodymium, and 5% praseodymium, with some samarium and gadolinium, or distinctly more lanthanum and less neodymium and heavies as compared to commercial monazite. The europium content was at least double that of a typical monazite.