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Rare Metals (RM) include Niobium (Nb), Tantalum (Ta), Lithium (Li), Beryllium (Be), Cesium (Cs) etc. and Rare Earths (RE) include Lanthanum (La) to Lutetium (Lu) besides Scandium (Sc) and Yttrium (Y). These metals are strategic in nature with wide application in the nuclear and other high tech industries such as electronics, telecommunication, information technology, space, defense etc. RMRE investigation group has been carrying out investigations for the last six decades in favourable geological environments to establish the resource base of these metals. Important minerals of these metals are beryl (Be), lepidolite (Li), spodumene (Li), amblygonite (Li), columbite-tantalite (Nb-Ta), pyrochlore (Nb) and xenotime (Y and REE).
Occurrence
The minerals beryl, columbite-tantalite, lepidolite, spodumene, amblygonite etc. generally occur in the pegmatite belts in different states of India viz. Rajasthan, Bihar, Andhra Pradesh, Karnataka, Odisha, Chhattisgarh, Madhya Pradesh and Tamil Nadu. Pyrochlore occurs in carbonatite complexes whereas xenotime occurs in the riverine placers in Central India. The metal content of such minerals in India are as follows:
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1 |
Beryl |
10 - 13 % BeO |
| 2 |
Columbite-Tantalite |
26 - 80 % Nb2O5 |
| 6 - 70 % Ta2O5 |
| 3 |
Lepidolite |
3 - 5 % Li2O |
| 4 |
Spodumene |
4 - 6% Li2O |
| 5 |
Amblygonite |
8 - 10% Li2O |
| 6 |
Xenotime |
32 - 40% Y2O3 |
| 18 - 19% HREE |
Recovery Operations
Small scale recovery operations (3-5 tonnes per annum) are carried out to recover columbite-tantalite from pegmatite gravels incidental to prospecting. Columbite-tantalite is heavy (sp. gravity 5.3-7.8) and therefore gravity separation is used to separate it from the other pegmatitic minerals such as quartz and feldspar which are lighter (sp. gravity 2.8). In the past, several recovery plants were set-up in Bihar Mica Belt, Jharkhand and Bastar-Malkhangiri Pegmatite Belt, Chhattisgarh for the recovery of columbite-tantalite.In addition, recovery plants were set-up at Marlagalla, Mundur and Arehalli in Karnataka for the recovery of columbite-tantalite with spodumene as co-product. Beryl, which occurs in these pegmatites is generally hand sorted and recovered, based on colour, lustre and hexagonal crystalline form.At present these operations are being carried out in Mandya district, Karnataka and Jharsuguda district, Odisha.
Nb-Ta recovery plants at Marlagalla, Mandya district,Karnataka and Jangapara, Jharsuguda district
Xenotime, a Y and REE bearing phosphate mineral, is associated with riverine placers in Siri River and Deo River in Chhattisgarh and Jharkhand respectively. Xenotime is a heavy mineral (sp. gravity 4.5) associated with sands (quartz and feldspar) in the rivers traversing Chhotanagpur Granite Gneissic Complex (CGGC). The other heavy minerals include monazite, zircon, ilmenite, magnetite, garnet, columbite etc. Presently xenotime bearing polymineralic concentrate is recovered (~6 tonnes per annum) from riverine placers in Jashpur district, Chhattisgarh.
Xenotime bearing placer bar along Siri river and recovery plant at Kunkuri, Chhattisgarh
In addition, carbonatites and alkaline rocks of Gujarat and Rajasthan are being explored around Ambadongar and Siwana Ring Complex for RMRE mineralization in hard rocks.
AMD purchases tantalum, niobium and beryllium ores as well as Nb-Ta bearing slag, generated by tin plants and sale the lepidolite (lithium minerals) at the price fixed by Government of India.