Where to find goldGold is often found in underground veins of quartz and, less frequently, in other minerals such as pyrite, granite and mica slate. The veins can be anything from half an inch to several feet wide. 80% of the gold that’s produced today is mined from such sources (the rest is ‘alluvial’ gold – see below). Knowing where to mine involves ‘chasing’ the gold-bearing veins on the surface, back underground. It’s been estimated that in the past 500 years, about 100, 000 tonnes of gold have been mined, but even this amount would only fill a cube with 17 m sides. The world’s biggest gold producer is South Africa, where gold mines are sunk over 3,000 metres deep into the earth.