Gypsum : The Mineral of utmost necessity in Cement Manufacture , which practically has no alternative for its use in Cements

Gypsum (CaSO4..2H2O) is used widely in various industries either as Gypsum i.e the Gypsum di-hydrate crystalline variety or as the Gypsum hemi hydrate, also known as Plaster of Paris (POP ) or Bassinite mineral ..
Selenite Gypsum is a colourless, transparent, naturally occurring crystalline variety of gypsum and is used extensively in Ceramic Industry and for manufacturing surgical grade Plaster of Paris, whereas alabaster is a fine-grained, massive variety, white or shaded in colour. The Silky and fibrous variety of gypsum is called satin spar.It also occurs in nature as Water soluble Natural anhydrite(CaSO4) as a massive or fibrous mineral. This variety does not much occur in India but countries like Turkey , Egypt , Oman , Thailand etc have substantial occurrence of Natural anhydrite .
In general the Gypsum that occurs in nature is called Mineral gypsum. In addition to Mineral Gypsum occurring in Gypsum Mines , . Gypsum . is recovered from salt pans during production of common salt in coastal region, particularly in Gujarat and Tamil Nadu. , this variety is known as Marine gypsum .The washed Marine gypsum with lower Chlorides (as NaCl content ) is usable in Cement Manufacture .
In India as per the NMI databasebased on UNFC system, the total reserves/resources of mineral gypsum inIndia as on 1.4.2015 have been estimated at 1,330million tonnes of which 37 million tonnes havebeen placed under ‘Reserves’ and 1,293 milliontonnes under ‘Remaining Resources’ category.Of the total reserves/resources, Fertilizer/Pottery grade accounts for about 80% andCement/Paint grade 13%. .The Unclassified and other grades together account for 5%resources. The remaining two percent of resourcesis shared by Surgical Plaster and Soil Reclamationgrades. .By States, Rajasthan alone accounts for81% resources, Jammu & Kashmir 14% and TamilNadu 2% resources. The remaining 3% resourcesare in Gujarat, Himachal Pradesh, Karnataka,Uttarakhand, Andhra Pradesh and MadhyaPradesh (ref 1).
India’s cement production capacity stood at around 502 million tonnes per year (mtpa) in 2018 and is expected to reach 550 million tonnes by 2025. Typically manufacture of Cement uses 2 to 4 % gypsum is used per ton of Cement . Thus the country requires to import substantial gypsum to cater to the requirements of Cement Industry . This has made the cement Industry to look at the usage of different Varieties of by product / Chemical / synthetic gypsum .
This paper discusses to begin with the role and necessity of use of Gypsum and assesses the available avenues of using other types of available chemical / by- product / Synthetic gypsum available in the country .