Customs exemption for fluorspar limits payable duty by exempting amounts above a prescribed ad valorem rate. Exemption for Fluorspar (Customs Tariff heading 25.29) exempts that portion of customs duty specified in the First Schedule which is in excess of 35 per cent ad valorem, effected under sub section (1) of section 25 of the Customs Act, 1962, and operative up to and inclusive of 29 February 1988.