How Miners Dig for Gold Miles Underground

Every day thousands of miners descend deep into the Earth’s crust in the hunt for gold. It’s a dark and dangerous world.

Gold mining at South Deep, the world's second-biggest deposit, would never be easy. Located an hour's drive west of Johannesburg, the resource holds 63 million ounces that formed in an ancient lake, now crystallized in rock, three kilometers (1.9 miles) underground. Gold Fields Ltd. has spent 29 billion rand ($2.5 billion) on the mine and has repeatedly missed ramp-up targets due to fatal accidents, mistakes and changing mining methods. A complex geological formation, seismic activity as well as the difficulty of operating high-powered diggers in deep tunnels has slowed progress. Now, armed with a new mining plan and costs under control, it says South Deep will operate at full capacity within five years, and will churn out the precious metal for at least the next 70 years.

Photographs by Waldo Swiegers/Bloomberg

Going Deep
Going Deep

Rocky Wyngaard drills a hole in a tunnel roof in the South Deep mine in Westonaria, South Africa, that will be used to fix wire netting to prevent falling rocks. Holes in the rock face are filled with explosives that break ore into rubble that's then transported to the surface through a series of dump trucks, chutes and lifts.

As Hot as Hades?
As Hot as Hades?

Liquid gold pours from a furnace into individual casting molds at South Deep's furnace. Some 500,000 ounces of gold are to be poured each year.

The Rough Stuff
The Rough Stuff

Gold is refined to about 85% purity on site before it's taken to Rand Refinery, in the east of Johannesburg, where it's processed to London Bullion Market standards of 99.99%.

Stocking Up
Stocking Up

Spare parts for heavy machinery are stacked high in a purpose-built workshop 2.6 kilometers underground. The repair factory has a footprint of about 11,500 square meters.

Dangerous Work
Dangerous Work

Working this far underground has significant risks. Some 23 people have been killed at the mine under Gold Fields's ownership, including nine in a single incident in 2008 when a lift cable snapped.

Hold On Tight
Hold On Tight

A bar is worth about $1.15 million at today's prices, making security a top concern.

Precarious Balance
Precarious Balance

Gold Fields expects South Deep's all-in sustaining costs to be about $900 an ounce starting in 2022, well below almost $1,300 today.

Bigger Diggers
Bigger Diggers

Gold Fields has purpose-built bigger tunnels to allow such machines to move more easily around the mine.  The company has recently changed the way it mines and now uses larger, more efficient diggers that save costs.

Getting Support
Getting Support

Waste rubble is packed in bags and placed in abandoned areas to provide support to the mine's structure.

Small Payout
Small Payout

A ton of ore produces about 5 grams of gold, equal to the weight of a U.S. nickel or a British 20-pence coin.