The mighty river Brahmaputra and its tributaries are filled with rain water during monsoon season, which often creates moderate to severe flood situation in Assam. This is also the peak season of multiplication of a particular half-moon shaped snail species locally known as Junai samuk. During the era of Ahoms, who migrated from Thailand and ruled Assam for more than 600 years, people used to collect Junai samuk and a long tailed conical shaped snail from river banks, ponds and beels. The snails were sun dried for several days and shells were seprated from the dried body and stored. The shells were ground and this powder formed calcium carbonate or lime.