Rock Hunting In Alabama. How to Pan for Gold in Your Backyard. How to Find Gold in Quartz. Environmental Hazards of Limestone Mining. How to Identify a Gold Bearing Area.
Gold Smelting Process. How Are River Rocks Formed? Nevertheless, gold accounts for a few parts per billion of the mass of the Earth's crust. While it's not economically feasible to extract much gold, there are about 1 million tons of gold in the top kilometer of the Earth's surface. The abundance of gold in the mantle and core is unknown, but it greatly exceeds the amount in the crust.
Attempts by alchemists to turn lead or other elements into gold were unsuccessful because no chemical reaction can change one element into another. Chemical reactions involve a transfer of electrons between elements, which may produce different ions of an element, but the number of protons in the nucleus of an atom is what defines its element. All atoms of gold contain 79 protons, so the atomic number of gold is Making gold isn't as simple as directly adding or subtracting protons from other elements.
The most common method of changing one element into another transmutation is to add neutrons to another element. Neutrons change the isotope of an element, potentially making the atoms unstable enough to break apart via radioactive decay.
Japanese physicist Hantaro Nagaoka first synthesized gold by bombarding mercury with neutrons in While transmuting mercury into gold is easiest, gold can be made from other elements—even lead! Soviet scientists accidentally turned the lead shielding of a nuclear reactor into gold in and Glenn Seabord transmuted a trace of gold from lead in Thermonuclear weapon explosions produce neutron captures similar to the r-process in stars.
While such events are not a practical way to synthesize gold, nuclear testing did lead to the discovery of the heavy elements einsteinium atomic number 99 and fermium atomic number Actively scan device characteristics for identification.
Use precise geolocation data. Select personalised content. Create a personalised content profile. You will even find gold in the oceans, which contain more than 20 million tons of the precious yellow metal. But the gold there is so diluted, it is presently infeasible to collect it from water profitably.
Flakes or even entire nuggets get sorted out in streams of water that originate near or run through these rich gold deposits. These gold deposits are found all over the world, with several notable sites in the United States. Included are north Georgia, the western Carolinas, the Rockies, parts of Nevada, and much of California. One of the first gold rushes came in when gold was found in North Carolina.
About 30 years later, a major gold rush hit northern Georgia. It kicked off the great California Gold Rush, luring thousands of prospectors to the region throughout the mids. Many of the early discoveries of gold came by way of panning for it in rivers or even finding nuggets lying on the ground.
Yet commercial-scale operations required heavy mining activity. That became big business in places like northern California, in the Sierra Nevada Mountains, and western Nevada. Gold was discovered in the Yukon Territory around the turn of the 20th century, drawing countless prospectors there, too. The United States has been fortunate to see several significant gold deposits. They are classified according to their use. Some industrial minerals are used as sources of important chemicals e.
Some are used for building materials e. Others are used for making fertilizers e. Still others are used as abrasives e. A geologist defines a mineral as a naturally occurring inorganic solid with a defined chemical composition and crystal structure regular arrangement of atoms.
Minerals are the ingredients of rock , which is a solid coherent i. There are three classes of rock, igneous, sedimentary, and metamorphic. Igneous rocks form by cooling and solidification of hot molten rock called lava or magma. Lava solidifies at the surface after it is ejected by a volcano, and magma cools underground.
Metamorphic rocks form when the shape or type of minerals in a preexisting rock changes due to intense heat and pressure deep within the Earth. Ore is rock with an enrichment of minerals that can be mined for profit. Sometimes ore deposits locations with abundant ore can be beautiful, such as the giant gypsum crystals at the amazing Cave of the Crystals in Mexico see Figure Giant Gypsum Crystals.
Mining of some metals, such as aluminum and iron, is profitable at relatively small concentration factors, whereas for others, such as lead and mercury, it is profitable only at very large concentration factors. The metal concentration in ore column 3 in Table Enrichment Factor can also be expressed in terms of the proportion of metal and waste rock produced after processing one metric ton 1, kg of ore.
Iron is at one extreme, with up to kg of Fe metal and only kg of waste rock produced from pure iron ore, and gold is at the other extreme with only one gram. Minerals are everywhere around us. For example, the ocean is estimated to contain more than 70 million tons of gold. Yet, it would be much too expensive to recover that gold because of its very low concentration in the water. Minerals must be concentrated into deposits to make their collection economically feasible.
A mineral deposit containing one or more minerals that can be extracted profitably is called an ore. Many minerals are commonly found together e. Because various geologic processes can create local enrichments of minerals, mineral deposits can be classified according to the concentration process that formed them.
The five basic types of mineral deposits are: hydrothermal, magmatic, sedimentary, placer and residual. Hydrothermal mineral deposits are formed when minerals are deposited by hot, aqueous solutions flowing through fractures and pore spaces of crustal rock. Many famous ore bodies have resulted from hydrothermal deposition, including the tin mines in Cornwall, England and the copper mines in Arizona and Utah.
Magmatic mineral deposits are formed when processes such as partial melting and fractional crystallization occur during the melting and cooling of rocks.
Pegmatite rocks formed by fractional crystallization can contain high concentrations of lithium, beryllium and cesium. Layers of chromite chrome ore were also formed by igneous processes in the famous Bushveld Igneous Complex in South Africa. Several mineral concentration processes involve sedimentation or weathering. Water soluble salts can form sedimentary mineral deposits when they precipitate during evaporation of lake or seawater evaporate deposits.
Important deposits of industrial minerals were formed in this manner, including the borax deposits at Death Valley and Searles Lake, and the marine deposits of gypsum found in many states.
Minerals with a high specific gravity e. The most famous gold placer deposits occur in the Witwatersrand basin of South Africa. Residual mineral deposits can form when weathering processes remove water soluble minerals from an area, leaving a concentration of less soluble minerals. The aluminum ore, bauxite, was originally formed in this manner under tropical weathering conditions. The best known bauxite deposit in the United States occurs in Arkansas. Ore deposits form when minerals are concentrated—sometimes by a factor of many thousands—in rock, usually by one of six major processes.
These include the following: a igneous crystallization , where molten rock cools to form igneous rock. This process forms building stone such as granite, a variety of gemstones, sulfur ore, and metallic ores, which involve dense chromium or platinum minerals that sink to the bottom of liquid magma. Diamonds form in rare Mg-rich igneous rock called kimberlite that originates as molten rock at — km depth where the diamonds form and later moves very quickly to the surface, where it erupts explosively.
The cooled magma forms a narrow, carrot-shaped feature called a pipe. Diamond mines in kimberlite pipes can be relatively narrow but deep see Figure A Diamond Mine.
It involves hot, salty water that dissolves metallic elements from a large area and then precipitates ore minerals in a smaller area, commonly along rock fractures and faults. Molten rock commonly provides the heat and the water is from groundwater, the ocean, or the magma itself. The ore minerals usually contain sulfide S 2- bonded to metals such as copper, lead, zinc, mercury, and silver. Actively forming hydrothermal ore deposits occur at undersea mountain ranges, called oceanic ridges, where new ocean crust is produced.
These gold and diamond ore bodies are called placer deposits. Other sedimentary ore deposits include the deep ocean floor, which contains manganese and cobalt ore deposits and evaporated lakes or seawater, which produce halite and a variety of other salts.
There are two kinds of mineral mines, surface mines and underground mines. The kind of mine used depends on the quality of the ore, i.
Surface mines include open-pit mines , which commonly involve large holes that extract relatively low-grade metallic ore see Figure Open Pit Mine , strip mines , which extract horizontal layers of ore or rock, and placer mines , where gold or diamonds are extracted from river and beach sediment by scooping up dredging the sediment and then separating the ore by density.
Large, open-pit mines can create huge piles of rock called overburden that was removed to expose the ore as well as huge piles of ore for processing. Underground mines, which are used when relatively high-grade ore is too deep for surface mining, involve a network of tunnels to access and extract the ore. Processing metallic ore e. The fine-grained waste produced from processing ore is called tailings. Slag is the glassy unwanted by-product of smelting ore.
Many of the nonmetallic minerals and rocks do not require chemical separation techniques. Mineral ores are found in just a relatively few areas, because it takes a special set of circumstances to create them. Therefore, the signs of a mineral deposit are often small and difficult to recognize. Locating deposits requires experience and knowledge.
Geologists can search for years before finding an economic mineral deposit. Deposit size, its mineral content, extracting efficiency, processing costs and market value of the processed minerals are all factors that determine if a mineral deposit can be profitably developed. For example, when the market price of copper increased significantly in the s, some marginal or low-grade copper deposits suddenly became profitable ore bodies. After a potentially profitable mineral deposit is located, it is mined by one of several techniques.
Which technique is used depends upon the type of deposit and whether the deposit is shallow and thus suitable for surface mining or deep and thus requiring sub-surface mining.
Surface mining techniques include: open-pit mining, area strip mining, contour strip mining and hydraulic mining. Open-pit mining involves digging a large, terraced hole in the ground in order to remove a near-surface ore body.
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