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Monazite is an important ore for thorium, [8] lanthanum, and cerium. [9] It is often found in placer deposits. India, Madagascar, and South Africa have large deposits of monazite sands. The deposits in India are particularly rich in monazite. Monazite is radioactive due to the presence of thorium and
Monazite can form in fabrics caused by deformation. Monazite may be present as elongate grains aligned in foliation. It can be interpreted that either the monazite formed before the shearing and was aligned during shearing, or formed at the same time as the shearing. [3] It thus provides an upper limit of the shearing age.
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.
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-(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) .
In the study of metamorphic petrology, uranium–thorium–lead dating of monazite (monazite geochronology) is an effective method to determine the P-T history. [ 29 ] [ 30 ] Monazite is a phosphate mineral containing light rare-earth-elements (LREE) that occurs in a wide range of rock types. [ 31 ]
Undulose extinction or undulatory extinction is a geological term referring to the type of extinction that occurs in certain minerals when examined in thin section under cross polarized light. As the microscope stage is rotated, individual mineral grains appear black when the polarization due to the mineral prevents any light from passing through.
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.