Move takes the group’s total investment in the Indian city of Surat, which has the largest concentration of diamond skilled workers in the world, to $15 million.
Transactions must be fully backed by physical metal and settled on the same day to observe Islam's distinction between real economic activity and speculation.
Situation has worsened as a result of a shortage of new discoveries, cost cutting measures and miners digging out higher-grade material for a short-term gain, say experts.
Cameroon is allowing conflict diamonds from the Central African Republic to cross over its borders and into the legal supply chain due to poor controls, smuggling and corruption, a new report shows.