The stock sank as much as 25% in Johannesburg, wiping out about 15.2 billion rand ($824 million) of its market value.

According to Sprott, there is some additional room for prices to move in the short term.

The Gravelotte mine, operational between 1929 and 2002, was one of the world's largest emerald mines in the 1950s and 1960s .

MMG has been hunting for copper assets for more than a year, amid a surge in demand for the metal needed in green energy transition.

The West African country has rich mineral reserves of diamonds, gold and iron ore.

The defendants had been accused of deceiving investors about the value of Rio Tinto Coal Mozambique.

To improve the power supply, CMOC has been looking to tap hydropower projects and other new energy sources.