How Gold Is Mined: From Rock to Bar

Gold exploration starts with geology: gold forms in quartz veins and alluvial deposits, often associated with volcanic activity. Geologists map rock formations, sample soil and rock, and use geophysics to find anomalies — then drill core samples to test whether the gold is there in economic quantities.

Most exploration fails: the odds of a prospect becoming a mine are low, and the process takes years and large amounts of money. A discovery today might become a producing mine in ten or fifteen years — which is why gold supply responds so slowly to price rises.

Large, near-surface deposits are mined by open pit: enormous terraced holes, worked by trucks the size of houses, moving hundreds of thousands of tonnes of rock a day. The biggest open-pit gold mines — Muruntau in Uzbekistan, Super Pit in Australia — are among the largest holes humans have ever dug.

Deeper deposits are mined underground, through shafts and tunnels, at far higher cost. South Africa's mines are the deepest in the world, reaching nearly 4 kilometres down, where rock temperatures are high enough to need refrigeration. Underground mining is more selective — it targets rich veins — but it is slower and more dangerous.

Gold ore typically contains just a few grams of gold per tonne of rock — sometimes less than one gram. The rock is crushed, ground to powder, and treated to separate the gold. The standard method is cyanide leaching: a dilute cyanide solution dissolves the gold, which is then recovered onto carbon and smelted into bars.

Cyanide leaching is efficient but controversial: cyanide is toxic, and spills have caused serious environmental damage. The industry has improved containment and detoxification, but the risk remains — and it is one reason gold mining faces growing scrutiny. Artisanal miners often use mercury instead, which is more dangerous still.

China is the world's biggest gold producer, followed by Australia, Russia, the United States and Canada. The biggest mines include Muruntau (Uzbekistan), Grasberg (Indonesia), Carlin (USA) and the Super Pit (Australia). Africa's biggest producers are Ghana, Mali, Burkina Faso and South Africa — the last once dominant, now in decline as its deep mines age.

Annual mine production is roughly 3,000 tonnes — about 1–2% of all the gold ever mined. That slow growth is why gold holds its value: unlike paper money, its supply cannot be expanded quickly, whatever the price.

Gold mining is environmentally expensive: it moves enormous amounts of rock, uses large quantities of water and energy, and produces toxic waste. A single gold ring can generate tonnes of mining waste. Artisanal mining — which produces a significant share of the world's gold — is often unregulated and uses mercury, poisoning miners and rivers.

The industry is under pressure to improve: better waste management, water recycling, and certification schemes for responsibly mined gold. Recycled gold — from old jewellery and electronics — now supplies a significant share of the market and avoids mining entirely.