The Union Cabinet on Thursday gave approval in principle to the long-awaited National Mineral Policy. The new policy is likely to attract foreign direct investment to the tune of $250 million per annum. It is expected open up country's huge untapped mineral deposits besides helping mineral-rich states earn more revenue as it talks about progressing towards an ad-valorem duty structure. An amendment Bill would be introduced during the Budget Session to bring about suitable amendments in the Mines and Minerals (Development and Regulation) Act, 1957.