How Gold Is Mined & Refined
The production of gold is a lengthy process that involves a lot of careful planning, analysis and industry. Once a sufficient source is located, extraction methods are determined by the composition of the gold ore, as well as the geological features and legal precepts that govern the site. After miners extract gold ore, it is refined into pure form and formed into gold bricks for transport.
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Creating the Mine
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After geologists use satellite surveys or chemical testing to find ore deposits, scientists use computers to create a plan of the mine electronically in order to ensure safe and efficient extraction. In addition, mining companies must obtain legal permits permitting them to carry out their work. Construction of the mine revolves around any existing geological barriers, as well as the physical composition of the gold ore.
Extraction of Gold From Low-grade Ore
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Most gold mining in the United States is extracted through open-pit mining, or above ground. Throughout this process, gold ore is separated into two main categories and dispatched accordingly for refinement: low-grade ore and high-grade ore. Low-grade ore, containing less amounts of additional minerals, involves a simpler process of refinement. After being broken down into small chunks, the ore is distributed over a series of pads and doused with a cyanide dilute, which dissolves the gold throughout the heap.
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Extraction of Gold From High-grade Ore
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High-grade ore exists in a number of forms, and there are a variety of refinement processes available depending upon the composition of each. For all types, the ore is pulverized and ground into a powder. Workers use one of three types of chambers called recovery circuits that provide further processing before the cyanide dilute is used, as with the low-grade ore. These recovery circuits use heat and additional solutes in order to recover the gold from the ore.
Creating Gold Bars
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After the gold-containing cyanide solution is recovered from either type of ore, workers complete a series of steps in order to extract pure gold. First, the gold is extracted from the cyanide solution by combining it with carbon, which absorbs the gold while the cyanide solution is recycled for future use. Next, using special chemicals, the carbon is stripped from the gold and the product is purified using an electrolytic chamber. Finally, gold is melted down and pressed into gold bars. These bars are either destined for storage or are purchased for further production into jewelry or other special goods.
Reclamation
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The final step of gold production with regards to mining is reclamation, where mining companies are responsible for restoring the land they have worked on. This process takes a number of forms, depending upon the intensity of the process, budget issues, legal contracts and associated legislation.
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References
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