Rare Metal and Rare Earth Investigation : Atomic Minerals Directorate

Rare Metal and Rare Earth Investigation

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 exploration for the last seven decades in favourable geological domains to establish the resource base of these metals. Important minerals of rare metals are beryl (Be), lepidolite (Li), spodumene (Li), amblygonite(Li), columbite-tantalite (Nb-Ta), pyrochlore (Nb) and rare earth bearing minerals are xenotime (Y and REE), bastnaesite (LREE), monazite (LREE), synchysite (LREE), parasite (LREE), florencite (LREE) etc.

The rare metal minerals beryl, columbite-tantalite, lepidolite, spodumene 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 and bastnaesite occurs in carbonatite complexes whereas xenotime occurs in the riverine placers. The metal content of such minerals in India are as follows:

1	Beryl	10 - 13 % BeO
2	Columbite-Tantalite	26 - 80 % Nb₂O₅
2	Columbite-Tantalite	6 - 70 % Ta₂O₅
3	Lepidolite	3 - 5 % Li₂O
4	Spodumene	4 - 6% Li₂O
5	Amblygonite	8 - 10% Li₂O
6	Xenotime	32 - 40% Y₂O₃
6	Xenotime	18 - 19% HREE
7	Bastnaesite

Pilot scale plants are operated (nearly 2 tonnes per annum) to collect columbite-tantalite from pegmatite gravels incidental to prospecting. Columbite-tantalite is heavy (sp. gravity 5.3-7.8) and hence gravity concentration techniques are adopted to separate it from the other pegmatitic minerals such as quartz and feldspar which are lighter (sp. gravity 2.8). In the past, several pilot scale plants were set-up in Bihar Mica Belt, Jharkhand and Bastar-Malkhangiri Pegmatite Belt, Chhattisgarh for the collection of columbite-tantalite. In addition, pilot scale plants were set-up at Marlagalla, Mundur and Arehalli in Karnataka for the collection of columbite-tantalite with spodumene as co-product. Beryl, which occurs in these pegmatites is generally hand sorted and collected, based on colour, lustre and hexagonal crystalline form. At present these operations are being continued in Mandya district, Karnataka and Jharsuguda district, Odisha.

Nb-Ta collection plants at Marlagalla, Mandya district,Karnataka and Jangapara, Jharsuguda district

Xenotime, a Y and REE bearing phosphate mineral, is found in the 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 collected (~8 tonnes per annum) from riverine placers by operating a pilot scale plant in Jashpur district, Chhattisgarh.

Xenotime bearing placer bar along Siri river and pilot scale plant at Kunkuri, Chhattisgarh

In addition, Ambadungar carbonatite complex, Gujarat and HREE bearing per-alkaline rocks of Siwana Ring Complex, Rajasthan are being explored for RMRE mineralization in hard rocks. AMD purchases tantalum, niobium and beryllium ores as well at notified price fixed by Government of India.