STATUS OF MINERAL DEVELOPMENT IN SIKKIM
The Geological Survey of India (GSI) has completed systematic geological mapping of 90 % of accessible land on 1:50000 scale and carried out mineral exploration mostly around parts of South, West and East Sikkim. The State Department of Mines, Minerals and Geology has been working on site specific geological & geo - technical study, on a prioritized basis, both the agencies have found large deposits of low value - high bulk minerals besides base metal occurrences mostly within the Daling Group of rocks called Gorubathan Formation. The activities of the GSI and the State Department of Mines and Geology are reviewed periodically and monitored during Central Geological and State Geological Board meetings. Despite efforts by the Department of Mines, Mierals & Geology, Government of Sikkim and the GSI, large areas of the State remains unexplored. However, occurrence of the following minerals have been studied.
Coal: There are no coal fields as such in Sikkim, however coal occurrences are widespread in the so called ' Rangit Tectonic Window' zone. Detailed studies by G.S.I. around Namchi, South Sikkim, established a reserve of 1.40 Lakh tonnes of coal. The State DMG carried on further studies on coal & promising areas have been identified. The proximate analysis of coal from those areas show following compositions :-
| Location |
Fixed Carbon |
Ash % |
VM % |
Moisture % |
| Reshi ( South Sikkim) |
49.70 |
43.30 |
4.40 |
2.60 |
| Sikkip |
68.40 |
25.70 |
2.20 |
3.70 |
| Nandugaon |
69.40 |
24.30 |
3.20 |
3.10 |
| Namchi |
53.40 |
39.50 |
3.40 |
3.70 |
Coal Reserve of nearly 70,000 tonnes at Reshi ( South Sikkim) has been established and coal samples from the area was analyzed at the CMPDIL, Ranchi for test domestic consumption in the form of co - cakes/ coal briquettes. The Institute developed honey - comb coal briquettes using 75 % Sikkim coal plus other high volatile coal from elsewhere and oxidants / additives. The thermal yield of the briquettes so developed comes to 5,2000 K.Cal / Kg which is better than the thermal tiled of firewood (3,500 K/Cal/Kg). Besides such test, the departmental Scientists developed indigenous hand made briquettes successfully by blending local coal with clay, and additives.
Quartzite: Occurences of high grade quartzite with over 90 % silica has been found in parts of East, West & South Sikkim. The quartzite occurrence at Ranikhola - Mansari area of West Sikkim was mined commercially, and the mine is being considered for revival. Estimated mineable reserve of some 70,000 tonnes at the area lies unexploited. The overall chemical composition variation according to CG & CRI, Calcutta is as follows.
| SiO2 |
Al2O3 |
CaO |
MgO |
Fe2O3 |
TiO2 |
K2O |
Na2O |
LOI |
91.68
to 98.97 |
0.37
to
2.98 |
0.02
to
1.68 |
Trace
to
0.89 |
0.06
to
2.11 |
Trace |
Trace
to
0.89 |
0.03
to
0.95 |
0.18
to
0.88 |
Talc: Talc in Sikkim has been found as intercalations in quartzite deposit of Ranikhola - Mansari area of West Sikkim. As estimated reserve of about 80,000 tonnes of the mineral lie in the leased area of M/S Sikkim Pvt. Ltd. and some more are being mined by rat hole mining by villagers for export to Siliguri. Composition of talc in the area is as follows.
| SiO2 |
MgO |
CaO |
Al2O3 |
Fe2O3 |
Alkalies |
LOI |
45.92
to
63.60 |
24.45
to
37.45 |
0.10
to
1.79 |
1.60
to
7.86 |
0.20
to
3.04 |
0.25
to
2.00 |
1.00
to
5.00 |
Dolomite & Limestone: Sikkim has extensive deposits with bands of dolomite limestone in Rangit Valley Tectonic Window. Exploratory work has been done by G.S.I. and the State DMG. Samples from the area show the following variation of chemical composition.
| CaO |
Al2O3 |
Fe2O3 |
SiO2 |
MgO |
Na2O |
K2O |
LOI |
30.88
to
48.35 |
1.76
to
5.07 |
1.32
to
5.42 |
7.88
to
32.27 |
0.97
to
1.72 |
0.13
to
1.04 |
0.04
to
1.79 |
25.45
to
88.12 |
Marble: Sikkim is endowed with sizeable deposits of marble around Tsungthang, Tsongo and Tolong. Much attention was paid to this mineral for viable commercial exploitation. Presently the mineral is being tested and studied in detail for use as cut and polished slabs. The test samples compare with the marble slabs in the market. Other possible use of this resources is in the manufacture of cement, calcium carbide, chemicals etc.
Base Metal: As regards to ploy metalliferous deposits in the State, Copper- Lead- Zinc deposit at Bhotang, Rangpo, has been under exploitation by Sikkim Mining Corporation. Other base metal deposit under consideration for exploitation by the Government is the Dikchu Copper - Zinc project. The techno - feasibility study of the project was done by the Mineral Exploration Corporation of India. The total ore reserve, according to MECL, is about 0.45 million tonnes containing 2.82 % Cu and 0.90 % Zn. Out of the total ore reserve, about 0.30 million tonnes contains an average of 3% Cu and 1 % of which falls under the developed and proved category. The investigated lode extends for about 564 metres in length, 100 metres in vertical depth & 1.25 metres in thickness. The test carried out on bulk samples of ore from Dikchu gave 90 - 93 % recovery copper in the concentrate.
Graphite: Graphite in Sikkim occurs over parts of West and North Districts. Workable occurences are located at Chitre - Dariely & Dentam - Uttarey area of West Sikkim. The graphite is made up of 40 - 60 % fixed carbon. Beneficiation is necessary for commercial exploitation.
Sillimanite: Investigation of sillimanite around head waters of Roathak Khola show occurences of the mineral in the form of boulders and in - situ lensoidal bodies. The boulders alone show a tentative reserve of over 1000 tonnes. Samples from the area on analysis show mineral falling within grade II. Reported occurences of Sillimanite / Kyanite bearing schist in the high grade biotite of Changey Khola needs further studies.
Thermal Springs: There are atleast eight known thermal springs in Sikkim. Of them, Phurtsachu, Borong and Polot in South Sikkim, Yumthang, Tarum and Tolung of North Sikkim are well known ones. The springs are being monitored from time to time unlike the perennial source of cold springs which are monitored and water tested frequently. The physico - chemical composition of some of the hot springs are as follows.
| Parameters |
Yumthang |
Tarum |
Phurtsachu |
| Flow Rate |
645 Lt / hr |
4500 Lt / hr |
- |
| Water Temp. |
450 C |
500 C |
450 C |
| Water Colour |
Clear |
Clear |
Clear |
| Odour |
Highly Sulfurous |
Mildly Sulfurous |
Highly Sulfurous |
| Taste |
Salty, unpleasant |
Unpleasant |
Salty,unpleasant |
| Radio activity |
Background |
Background |
Background |
| Total Solids |
100 mg / lt |
100 mg / lt |
675 mg / lt |
| Total alkalinity |
140 mg /lt |
60 mg / lt |
- |
| Acidity |
- |
- |
256 mg / lt |
| Total Hardness |
8 mg / Lt |
20 mg / Lt |
252 mg / lt |
| Ca Hardness |
8 mg / Lt |
16 mg / Lt |
120 mg / lt |
| Sulphate |
37.08 mg / Lt |
41.20 mg / Lt |
24.7 mg / Lt |
| Phosphate |
0.04 mg / Lt |
0.20 mg / Lt |
0.20 mg / Lt |
| pH |
7.7 |
7.4 |
7.23 |
| Sodium |
3 ppm |
24 ppm |
5 ppm |
| Potassium |
0.5 ppm |
0.75 ppm |
1.15 ppm |
| Chloride |
17.5 mg / Lt |
7.60 mg / Lt |
111.39 mg / Lt |
Source: Department of Mines, Minerals & Geology, Government of Sikkim, Gangtok