Gold dates from the time of the supernova explosion that gave birth to the building blocks of our solar system. When it was created, the Earth included a tiny percentage of gold atoms, and over the aeons geologic processes have concentrated it into various nooks and crannies around the globe. The best of it is in the ancient Precambrian rocks in South Africa, where the deepest mines in the world extract it. In other regions of the world, gold can be gathered from younger sedimentary rocks that have been eroded off older Precambrian rocks. The American gold rush was this type of deposit. Now in Nevada, sedimentary rocks are leached on a truly vast scale to extract the gold.