Apple has said in the past that it does not directly buy, procure or source primary minerals, and it has been auditing its suppliers for several years.

The Grand Inga has long faced headwinds because of Congo’s history of corruption and the expected cost of the multiphase project.

The ZiG, short for Zimbabwe Gold, launched April 5 is backed by 2.5 tons of gold and $100 million in foreign currency reserves.

At least 54 workers died in mining-related accidents in South Africa last year.

The Saudi Arabia project is still a pilot and not yet at commercially viable levels, Ma'aden's CEO said.

Zimbabwe loses about $1.5 billion annually to smuggling of the precious metal.