A kilometre below a rock-strewn green mountain in western Saudi Arabia, half a dozen Saudi and Filipino miners in orange helmets and olive-green overalls are boring into the ore veins of the Al Amar gold mine. Others carefully plant explosives in the cracks, while ore-laden trucks move back up the labyrinthine shaft to an extraction plant sweltering under the desert sun far above.

Al Amar, 200km southwest of Riyadh, is one of five gold mines operated by Ma’aden, the Saudi mining company. Ma’aden produced 127,744 ounces of gold worth SR420m ($112m) last year, and is responsible for the bulk of Saudi Arabia’s production which last year reached 5.7 tonnes.