In 1848, the discovery of a gold nugget in northern California sparked the California Gold Rush, the largest mass migration in U.S. history. Today, the idea of finding gold holds the same allure. An LA Times article describes modern-day prospectors in the Mother Lode region of California searching for gold the old-fashioned way, using buckets and classifiers, hog pans and cradles. CNN reports that members of the Association of Gold Seekers of Biella, Italy, are searching the banks of the Elvo river for gold that has washed down from the melting glaciers of the Alps.
Many discoveries of large gold nuggets have been recorded, but few remain. Most were melted down into gold bars or gold coins. Bullionstar.com profiles the top five largest ‘named’ gold nuggets which are still in one piece and on display to the public:
- Pepita Canaã, Brazil: The Pepita Canaã gold nugget was found in the Serra Pelada gold mining region of Brazilian state of Pará in 1983. It has a gross weight of 60.82 kgs and contains 52.33 kgs of gold, or 1682 troy ounces of gold. The nugget was purchased by the Banco Central do Brazil in 1984, and is now on display in the Museu de Valores do Banco Central in Brazil.
- The Great Triangle, Russia: This gold nugget was found in the Miass area of the Russian Urals mountains in 1842. It has a gross weight of 36.2 kgs and a gold assay of 91%, meaning that it has a fine gold content of 32.94 kgs, or 1059 troy ounces of gold.
- Hand of Faith, Australia: This 27.66 kgs gold nugget was found in Kingower, Victoria, Australia in 1980. It is the largest gold nugget ever found using a metal detector and contains 875 troy ounces of gold. The Hand of Faith nugget was purchased by the Golden Nugget Casino in Las Vegas, Nevada, and is currently on display in the casino lobby.
- Normandy Nugget, Australia: This 25.5 kgs (820 ozs) gold nugget was found is 1995 in Kalgoorie, Western Australia. Assay analysis shows the Normandy Nugget to have a gold purity of between 80% and 90%.The Normandy Nugget was purchased by Normandy Mining, which is now part of Newmont Gold Corporation, and is currently on display in the museum of the Perth Mint.
- Ironstone’s Crown Jewel, California: This nugget is a single piece of crystalline leaf gold found in California in 1992. The gold was embedded in quartz rock, but most of the quartz was removed to reveal a single mass of gold weighing 44 troy pounds (16.4 kgs). The Ironstone nugget is now on display at a heritage museum in Ironstone Vineyards in California.
Modern gold mining takes advantage of technological advancements including Portable X-ray fluorescence (XRF) analyzers. XRF sampling techniques are aimed at mapping the distribution of gold and in particular, the various pathfinder elements associated with gold (silver, copper, zinc, nickel, mercury, arsenic and barium). It’s much easier to find the pathfinder elements than it is to find gold and once found, they can help determine if gold is nearby. Although these geophysical methods can be crucial for gold exploration, geochemical methods, including XRF, are the only methods that can measure concentrations of gold and other associated elements.
Read Identification of Lithology & Base Metal Anomalies – Pathfinders for Gold Exploration Using Thermo Scientific Portable XRF Analyzers to learn about the successful use of portable XRF analyzers in gold exploration.