Geopeko was the exploration arm of the Australian mining company, Peko-Wallsend Limited. From a start as a small copper miner in the Northern Territory, Geopeko's discoveries built Peko-Wallsend into one of Australia's premier mining companies. It was a leader in the development of the geological theories and technologies that underpin mineral discovery. Geologist John Elliston and geophysicist Lew Richardson built a team of earth scientists, technicians, and drillers that laid the foundation for the success. This is the story of that success, compiled by those who were responsible for it, with an analysis of why it was successful.