CAPE TOWN (miningweekly.com) – The world’s third-largest gold-mining company, AngloGold Ashanti, was moving closer to its goal of continuous gold mining at ultra depth using a method that could change the hard-rock mining paradigm globally, the company’s executive VP Mike MacFarlane said on Tuesday.

MacFarlane told the Investing in African Mining Indaba, which is being attended by a record number of 7 500 delegates, that mouth-watering grades of 25 g/t would be recoverable from depths of 5 km and more.

The technology could bring about a step-change in mining intensity, as mining would be done in a fifth of the time without any need to invest in new infrastructure.

The project got under way in 2010 with the aim of unlocking 100-million ounces of gold that cannot be mine conventionally.

“We haven’t invented anything. All we’re doing is putting existing technology together in creative ways,” MacFarlane said.

“We could be developing technology that is unique for deep underground mining in South Africa and we could be turning what appears to be a sunset industry into a sunrise industry.

“We believe that if we get this right, we could actually change the mining paradigm for deep hard-rock underground mines globally,” he said.

The tunnel boring that has been undertaken indicates that it can increase the pace of development from 3 m a day to as much 20 m a day.

The new way of gaining information about the orebody is also likely to be taken on.

When the method was tried in 1974 it stumbled, on failing to come up with appropriate backfilling.

But the ultrahigh-strength backfill to be used will dispense with the need to leave large pillar areas unmined in order to assure safety.

South Africa still has one of the biggest gold resources in the world, but that gold is at depth, which results in significant amounts of the precious metal having to be left in shaft pillars and stability pillars, because blasting upsets the ground conditions and creates seismicity.

The proposed new way of mining dispenses with blasting, keeps people away from the danger areas; facilitates mining round-the-clock every day of the year and refocuses on revenue.

Current wasteful mining practise is not considered sustainable, not only because it sterilises too much gold in the ground, but also because South Africa is not competitive with its peers in term of days worked and time at the face.

Global competitors mine 365 days a year and at only 5% to 10% dilution, compared with only 274 working days and high dilution in South Africa.

Greater depth also adds to travel time, which means that mineworkers in many deep South African gold mines end up spending too few hours at the face.