The groundwater is the only major source of drinking water in western part of Rajasthan, India. The study was carried out to locate and decipher hydrogeochemical reactions responsible for elevated concentration of fluoride. The concentration of fluoride ranged from 0.6 to 4.74 ppm in groundwater of study area. Since the area is a desertic terrain and no industries are present thus possibility of anthropogenic input of fluoride is all most negligible thus the enrichment of fluoride in groundwater is only possible due to rock-water interaction. The highly alkaline conditions indicated fluorite dissolution as major process responsible for high concentration of fluoride in Pokhran.