51�Թ�

But in the 1970s, new technology, including bigger dump trucks, made open-cut mining more competitive.

Rather than tunnelling into the ground, Mr Dunstan is open-cut mining, which involves scraping away a few inches of rock with an excavator, and then periodically investigating for opals.

Earlier this month, Steve Bywater, GCM's chairman, said that a Bangladeshi parliamentary standing committee had recommended that the country moves towards extracting coal reserves using open-cut mining methods.