The provisional duties are expected to be imposed by Oct. 15 while the investigation is due to be finalised in April 2021.

ISO 24016 is to be used for the grading and description of single unmounted polished diamonds of more than 0.25 carats.

The gold deposit in Siberia is estimated to contain a fifth of Russia's gold reserves.

According to the Swedish company, mineral studies determined the predominant Ni-sulphide mineral to be pentlandite.

The plan is expected to bring in 340 billion roubles ($4.5 billion) a year for the Russian government.

Industry sources said the market already had the tools needed for consumers willing to pay a premium for sustainable metal.