|Rare Metals (RM) and Rare Earth Elements (REE)|
|A rare-earth mineral is a mineral whose principal element is a rare earth element. Yttrium is found in almost all rare earth minerals. Rare earth minerals are usually found in association with alkaline to per-alkaline igneous complexes, in pegmatites associated with alkaline magmas and in or associated with carbonatite intrusives. Perovskite mineral phases are common hosts to rare earth elements within the alkaline complexes. Mantle derived carbonate melts also are carriers of the rare earths. Hydrothermal deposits associated with alkaline magmatism contain a variety of rare earth minerals.The following includes the relatively common hydrothermal rare earth minerals and minerals which often contain significant rare earth substitution:|
|Allanite is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare earth elements. It has the general formula Ca(Ce,La,Y,Ca)Al2(Fe2+,Fe3+)(SiO4)(Si2O7)O(OH).|
|Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, and chlorapatite, named for high concentrations of OH–, F–, or Cl– ions, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca5(PO4)3(OH, F, Cl), and the formulae of the individual minerals are written as Ca5(PO4)3(OH), Ca5(PO4)3F and Ca5(PO4)3Cl, respectively.|
|The mineral bastnäsite is one of a family of three carbonate-fluoride minerals. There is bastnäsite-(Ce) with a formula of (Ce, La)CO3F. There is bastnäsite-(La) with a formula of (La, Ce)CO3F. There is also bastnäsite-(Y) with a formula of (Y, Ce)CO3F. Most bastnäsite is bastnäsite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnäsite and the phosphate mineral monazite are the two largest sources of cerium and other rare earth elements.|
|Cerite is a complex mineral containing Cerium, formula Ce9Fe(SiO4)6(SIO3)(OH)3 from Sweden. There are also various varieties of Cerite in which some of the Cerium is replaced by other elements, e.g. Lanthanum dominated Cerite and Yttrium Cerite.|
|Fluocerite is a mineral, a cerium, lanthanum fluoride, formula (Ce,La)F3. It is recognized as two different minerals depending on the cation, fluocerite-(Ce) and fluocerite-(La). Both crystallize in the hexagonal system.|
|Gadolinite is a mineral of a nearly black color and vitreous luster, and consisting principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with formula:
(Ce,La,Nd,Y)2FeBe2Si2O10. Called gadolinite-(Ce) or gadolinite-(Y) depending on the prominence of the variable element composition (namely, Y if it has more yttrium, and Ce if it has more cerium).
|In geology, the mineral monazite is a reddish-brown phosphate containing rare earth metals and an important source of thorium, lanthanum, and cerium. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral: * monazite-Ce (Ce, La, Pr, Nd, Th, Y)PO4
* monazite-La (La, Ce, Nd, Pr)PO4
* monazite-Nd (Nd, La, Ce, Pr)PO4
* monazite-Pr (Pr, Nd, Ce, La)PO4
The elements in parentheses are listed in the order in which they are in relative proportion within the mineral, so that lanthanum is the most common rare earth in monazite-La, and so forth. Silica, SiO2, will be present in trace amounts, as will small amounts of uranium. Due to the alpha decay of thorium and uranium, monazite contains significant amount of helium, which can be extracted by heating. Monazite is an important ore for thorium, lanthanum, and cerium. It is often found in placer deposits. The deposits in India are particularly rich in monazite.
|Parisite is a rare mineral consisting of cerium, lanthanum and calcium fluoro-carbonate, Ca(Ce,La)2(CO3)3F2. Parisite is mostly parisite-(Ce), however when neodymium is present in the structure the mineral becomes parisite-(Nd).|
|Titanite or sphene is a calcium titanium nesosilicate mineral, CaTiSiO5. Trace impurities of iron and aluminium are invariably present. Also commonly present are rare earth metals including cerium and yttrium.|
|Xenotime is a Rare Earth phosphate mineral, whose major component is yttrium orthophosphate (YPO4). Occurring as a minor accessory mineral, xenotime is found in pegmatites and other igneous rocks, as well as gneisses rich in mica and quartz. Associated minerals include biotite and other micas, chlorite group minerals, quartz, zircon, certain feldspars, analcime, anatase, brookite, rutile, siderite, and apatite.|
|Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. Hafnium is almost always present in quantities ranging from 1 to 4%.|
|Zirconolite is a mineral, calcium zirconium titanate; formula CaZrTi2O7. Some examples of the mineral may also contain cerium, niobium and iron; the presence of the cerium would make the mineral radioactive. It is black or brown in color.|
|MINERAL RESOURCES IN INDIA|
|Rare metal mineralization occurs in diverse geological set ups. The primary mineralization can be classified as(a) felsic volcanic hosted,
(b) granite hosted,
(c) pegmatite hosted and
(d) alkaline ultramfic carbonatite complex hosted.
In India, Rare Earth Elements are produced principally from by-products of beach sand mining. The geological provinces favourable for RM/REE mineralization, which deserve attention, are as follows:
(a) Mica belt of Jharkhand,
(b) Bhilwara mica belt, Rajasthan,
(c) Tin belt of Orissa and Chhattisgarh,
(d) Chhotonagpur Gneissic Complex in Jharkhand and West Bengal,
(e) Nellore mica belt, Andhra Pradesh and
(f) Jalore and Sewaria granitoid terrain in Rajasthan,
(g) carbonatite and molybdenum bearing areas in Tamil Nadu and
(h) Sung valley, Meghalaya.