Exemption of excise duty

Dear friends

Please help me  we run iron ore beneficiation plant and under section 4 of the rule 4/2006 all ores are exmpted from excise duty but we buy low grade iron ore and convert it to high grade iron ore Does this amount to manufacturing but we purchase and sell IRON ORE itself so please advise me if this item is excempted from Excise duty 

also if there were any amendments to this rule at later stages 

shashi Kant Gupta