Depleting deposits may hit gypsum output

Time has come when the mining gypsum will have to be deep-seated as the reserves on the surface have depleted. If the present trend of consumption of gypsum continues, there will be no reserves available after 15 years. “The warning signals are clearly available”.

With a domestic market share of 95per cent, Rajasthan is the leading producer of gypsum having estimated reserves of over 75 million tonnes. The annual gupsum production (all in the state sector) is put at 2.25 million tonnes with both Rajasthan State Mineral Development Corporation (RSMDC) and RSMM producing 10 lakh tonnes each. The share of Fertiliser Corporation of India is put at 2.5 lakh tonnes per year.

The state government has taken a conscious decision not to permit gypsum mining in the private sector. However there are reports, not denied officially, that about 3 lakh tonnes of gypsum is illegally mined each year.“It is just not possible to stop the illegal mining as small gypsum deposits are found in agricultural lands” says a senior government official. The mineral is sometime found at depths of a mere 1.5 feet.

Gypsum is currently mined at Hanumangarh, Ganganagar, Bikaner, Barmer and Jaisalmer areas and it is sold by both RSMDC and RSMM at prices ranging between Rs 132 to Rs 150 per tonne (ex-pit). In the market, however,gypsum is fetching Rs 197 to Rs 260 per tonne.

Rough estimates show that the deep-seated reserves of gypsum may be in the region of 80 million tonnes spread over an area of 10 sq km in the Nagaur district of Rajasthan. The over-burden is put at 1:7 and the depth could easily be 50 meters to 70 metres. The mining cost will certainly be much higher but there is no way out. According to Ajay K Ahluwalia, general manager (mining) of RSMDC the mining cost in case of deep-seated gypsum may be not less than Rs 200 per tonne. “We are working on a plan and MECON has been asked to suggest how the mining could be made more cheaper” says the general manager.

On the surface too the high-grade of gypsum is now not available in large quantities. The only way to increase the grade is through blending, says Ahluwalia.

The mineral, hydrated calcium sulphate, occurs as selenite, alabaster and satinspar. Marine gypsum is also recovered from salt pans during the processing of common salt in the coastal regions. Theother type of gypsum (phospho) is obtained as a by product during the manufacture of phosphoric acid by wet process.