Bihar Sales Tax Act (19 of 1947) , S.13(5)— Minerals used in Atomic Energy Plants - Extraction, storage and supply controlled by Govt. - Under agreement assessee to extract and supply minerals only to Govt. at fixed price - Supply constitutes sale and is chargeable to Central Sales Tax Central Sales Tax Act (1956) , S.4— Central Sales Tax (Bihar) Rules 1957 , Rule12— Where the extraction, storage and supply of Beryl and Columbite minerals used in Atomic Energy Plants were controlled by the Govt. of India under the Atomic Energy Act and under an agreement the assessee was to extract and supply the minerals to the Govt. at fixed price and not to others unless permitted by the Govt. the supply held constituted sale and was liable to be assessed under the Central Sales Tax Act because, though the freedom of contract had been curtailed, the supply was under a free volition and there was no compulsory acquisition of the minerals under S. 8 of the Atomic Energy Act.