1. All these three cases raise the question relating to liability to tax under S.7 - A of the Tamil Nadu General Sales Tax Act, 1959 . In these cases, the dealer buys raw bones. The raw bones are converted into crushed bones. The process is done through breaking the bones in a disintegrator. In the process of breaking the bones into pieces of 3/8" and 5/8" bones, bone grist, bone - meal, fluff horns and hoof are obtained. Roughly 50 per cent of raw bone is obtained as crushed bone; 15 per cent of raw bone is obtained as bone grist; about 15 per cent is obtained as bone - meal; about 10 per cent is obtained as fluff; about 5 per cent is obtained as horn hoof. The rest becomes waste. The dealers in T.C. No. 337 of 1979 exported crushed bone, but all the three dealers sold bone - meal, bone grist, fluff and horn hoof locally. As far as export is