Gold is extremely rare: According to all geological experience it is found only in low concentrations in rocks. Its average concentration in the Earth's crust is 0.005 parts per million.
In the world, there are currently somewhere between 120,000 and 140,000 tonnes of gold 'above ground'. To visualise this imagine a single solid gold cube with edges of about 19 metres (about three metres short of the length of a tennis court). That's all that has ever been produced.
Divided amongst the population of the world there are about 23 grams per person, about 1.2 cubic centimetres each. This equates to about £155 - £215 worth per person on Earth, depending on the current price.
Gold still underground: Where it is known about with reasonable confidence, and can be extracted economically, un-mined gold appears on the books of mining companies as reserves. There remains as reserves about 40% of the total of gold above ground, i.e about 50,000 tonnes. South Africa has 50% of the world's known stock of un-mined gold.
