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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
Michel-Lévy interference colour chart issued by Zeiss Microscopy. In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope.
An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on. The section is then polished on both sides using a fine diamond paste until it has a thickness in the range of 2–12 μm.
In such cases, a thin section of the mineral is used and examined under polarized transmitted light with a petrographic microscope. Another device using this property to identify minerals is the dichroscope .
Extinction is a term used in optical mineralogy and petrology, which describes when cross-polarized light dims, as viewed through a thin section of a mineral in a petrographic microscope. Isotropic minerals, opaque (metallic) minerals, and amorphous materials (glass) do not allow light transmission under cross-polarized light (i.e. constant ...
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 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.