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Generally, ores of 5 parts per million (g/t) or greater grade will be extracted using underground mining and aim follow the gold bearing structure. [50] A gold mine can expect to extract ores of 1–2 parts per million (g/t) in an open pit mine due to the relatively lower operating costs of an open pit mine. [51]
An ore shoot is a hypogenic mass that is deposited in veins within a planar channel or lode, found in a shear or fault zone, fissure or lithologic boundary. [1] The ore shoot is the area of concentration which contains a primary ore along the veins present in the rock, and consists of the most valuable part of the deposit.
If performed on bullion to international standards, the method can be accurate on gold metal to 1 part in 10,000. If performed on ore materials using fusion followed by cupellation separation, detection may be in parts per billion. However, accuracy on ore material is typically limited to 3 to 5% of reported value.
Ore grade is about 0.20 to 0.25 ounces of gold per ton of rock. The gold mineralization is very finely disseminated: "invisible gold". Carlin–type gold deposits are sediment-hosted disseminated gold deposits. These deposits are characterized by invisible (typically microscopic and/or dissolved) gold in arsenic rich pyrite and arsenopyrite. [2]
Nuggets are also referred to by their fineness, for example "865 fine" means the nugget is 865 parts per thousand in gold by mass. The common impurities are silver and copper. Nuggets high in silver content constitute the alloy electrum. [5] The chemical composition of supergene gold nuggets can reveal the characteristics of the primary ore. [6]
High-grade gold ore from the Harvard Mine, Jamestown, California, a wide quartz-gold vein in California's Mother Lode. Specimen is 3.2 cm (1.3 in) wide. Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
A gold pan. Gold prospecting is the act of searching for new gold deposits. Methods used vary with the type of deposit sought and the resources of the prospector. Although traditionally a commercial activity, in some developed countries placer gold prospecting has also become a popular outdoor recreation. Gold prospecting has been popular since ...
Homestake high-grade gold ore, view is about 1.2 cm wide The gold ore mined at Homestake was considered low grade (less than one ounce per ton), but the body of ore was large. [ 8 ] Through 2001, the mine produced 39,800,000 troy ounces (43,700,000 oz; 1,240,000 kg) of gold and 9,000,000 troy ounces (9,870,000 oz; 280,000 kg) of silver.