ITC REFUND UNDER INPUT TAX CREDIT

if the firms selling or purchasing goods of precious stones like a loose diamond in India only.
the GSt return is regularly month wise basis. and that firms didn't supplies goods to outside India.
we are avail that input tax credit in set off manner.
so when it comes in ITC REFUND claim UNDER INPUT TAX CREDIT SCHEME for that firms without zero rated supply of goods and services ?
kindly answer this...