The Extraction of Valuable Minerals

Mining is the extraction of valuable minerals or other geological materials from the earth. Usually from an ore body, lode, vein, seam, reef or placer deposits. These deposits form a mineralized package that is of interest to the miner. Ores recovered by mining include, Metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel and clay. Mining is required to obtain any material that cannot be grown, or created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non renewable resources such as petroleum, natural gas, and water. Mining stones and metal has been a human occupation since prehistoric times. Modern mining processes involve prospecting for ore, analysis of the profit potential of a mine, extraction of the desired materials, and final reclamation of the land after the mine is closed. Mining operations almost always create a negative environmental impact, both during the mining activity and after the mine has closed. This is the reason why most of the world's nations have passed regulations to decrease the impact. Since the beginning of civilization, people have used stone, ceramics and, later, metals found close to the Earth's surface. These were used to make tools and weapons, from high quality flint found in northern France, southern England and Poland was used to create flint tools. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. Other hard rocks mined are collected for axes included greenstone.

The oldest-known mine on archaeological record is the Lion Cave, in Swaziland, which carbon dating shows to be about 43,000 years old. At this site Paleolithic humans mined hematite to make the red pigment ochre. Mines of a similar age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons and tools. There are countless different ways to mine witch include surface mining witch is done by removing surface vegetation, dirt, and layers of bedrock in order to reach buried ore deposits. Techniques of surface mining include, open pit mining, which is the recovery of materials from an open pit in the ground, quarrying, identical to open pit mining except that it refers to sand, stone and clay, strip mining, which consists of stripping surface layers off to reveal ore seams underneath, and mountaintop removal, usually to help with coal mining, which involves taking the top of a mountain off to reach ore deposits deep into the mountain. Finally, landfill mining involves sites where landfills are excavated and processed. Landfill mining has been thought of as a solution to dealing with long term methane emissions and local pollution. Another type of mining is Subsurface mining which is the method of digging tunnels or shafts into the earth to reach buried ore deposits.

The useful ore or the waste rock are brought up through tunnels and shafts. Underground mining can be classified by the type of access shafts used, the extraction method or the technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts, and shaft mining uses vertical access shafts. Mining in hard or soft rock require different techniques. Some other methods used are shrinkage stope mining which is mining upward, creating a sloping underground room. Another one is longwall mining witch is when you grind a long ore surface underground, and room and pillar mining which is removing ore from rooms while leaving pillars in place to support the roof of the room. Room and pillar mining often leads to retreat mining, witch is when supporting pillars are removed as miners retreat, allowing the room to cave in, and that allows more ore to be loosened.

Next we have highwall mining witch is another form of surface mining that evolved from auger mining. In Highwall mining, the coal seam is penetrated by a Push Beam Transfer Mechanism witch continuously mines while being propelled by hydraulics. A cycle includes sumping and shearing. As the coal recovery cycle continues, the cutterhead is progressively launched into the coal seam for 19.72 feet. Then, the Push Beam Transfer Mechanism automatically inserts a 19.72-foot long rectangular Push Beam into the center section of the machine between the Powerhead and the cutterhead. The Pushbeam system can penetrate nearly 1,000 feet into the coal seam. One patented Highwall mining system uses augers enclosed inside the Pushbeam that prevent the mined coal from being contaminated by rock debris during the conveyance process.

Using a video imaging or a gamma ray sensor the operator can see ahead projection of the seam rock interface and guide the continuous miner's progress. Highwall mining can produce thousands of tons of coal in contour-strip operations with narrow benches, previously mined areas, trench mine applications and steep dip seams with controlled water inflow pump system and a gas venting system. Heavy machinery is used in mining to explore and develop sites, to break and remove rocks of various hardness and toughness, to process the ore, and to carry out reclamation projects after the mine is closed. Bulldozers, drills, explosives and trucks are all necessary for excavating the landIn the case of placer mining unconsolidated gravel or alluvium is fed into machinery consisting of a hopper and a shaking screen, which frees the intended minerals from the waste gravel. Then the minerals are concentrated using jigs. Large drills are used to sink shafts, excavate stopes, and obtain samples for analysis. Trams are used to transport miners, minerals and waste rock. Lifts carry miners into and out of mines, and move rock and ore out, and machinery in and out, of underground mines. Huge trucks, shovels and cranes are employed in surface mining to move large quantities of ore. Processing plants utilize large crushers, mills, reactors, roasters and other equipment to consolidate the mineral rich material and extract the desired compounds and metals from the ore.