Pure gold is so ductile that a single ounce of it can be drawn out into a wire 80 kms long, five microns or five millionths of a metre thick, without breaking. If you did this to all of the existing gold in the world, it would wrap around the earth 11 million times!
Pure gold is also a very soft metal. It will scratch easily, and it’s therefore unsuitable in its pure state for use as coinage or jewellery. For these purposes it’s usually alloyed with other metals such as silver, copper and zinc.
Gold 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.
Gold is also often found deposited where a river widens, as well as on the downstream side of large boulders and rocks. The flow of the water slowing down allows any gold to fall to the riverbed under its own weight.
Credit : Open Learn
Picture Credit : Google
Leave a Reply