Diamond is the hardest and the most abrasive-resistant material known, making diamonds essential parts of the ceramic, electronic, and carbide valve industries. The beauty and brilliance of diamonds have made them the jewel of choice, ever since the art of cutting facets was developed in the 16th century. The South African diamond rush began in 1867 on the heels of the American gold rush and oil rush, in the appropriately named borough of Hopetown.