Mining and Drilling
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Wikipedia-Article "Mining"
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This article is about mineral extraction. "Mining" can also refer to installing explosive devices. See Mine for other meanings.
Mining is the extraction of valuable minerals or other geological materials from the earth, usually (but not always) from an ore body, vein, or (coal) seam. Materials recovered by mining include bauxite, coal, diamonds, iron, precious metals, lead, limestone, nickel, phosphate, rock salt, tin, and uranium. Any material that cannot be grown from agricultural processes must be mined. Mining in a wider sense can also include extraction of petroleum, natural gas, and even water.
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History
The oldest known mine in the archaeological record is the "Lion Cave" in Swaziland. At this site, which has a radiocarbon age of 43,000 years, paleolithic humans mined for the iron-containing mineral hematite, which they ground to produce the red pigment ochre. Sites of a similar age where Neanderthals may have mined flint for weapons and tools have been found in Hungary.
Another early mining operation was the turquoise mine operated by the ancient Egyptians at Wady Maghareh on the Sinai Peninsula. Turquoise was also mined in pre-Columbian America in the Cerillos Mining District in New Mexico, where a mass of rock 200 feet (60 m) in depth and 300 feet (90 m) in width was removed with stone tools; the mine dump covers 20 acres (81,000 m²).
Black gun powder in mining was first time used in a mineshaft under Banská Štiavnica, Slovakia in 1627.
Mining techniques
Mining techniques can be divided into two basic excavation types:
Extractive metallurgy
The science of extractive metallurgy is the study of extraction of valuable metals and minerals from their ores. Although extractive metallurgy is all-encompassing, mineral processing (or mineral dressing) is often the term used for the study of processing coal, industrial minerals and precious stones, as these are not metals.
Environmental effects
Modern mining companies in many countries are required to follow strict environmental and rehabilitation codes, ensuring the area mined is returned to its original state, or an even better environmental state than before mining took place. Past mining methods have had, and methods used in countries with lax environmental regulations continue to have, devastating environmental and public health effects. The result can be unnaturally high concentrations of some chemical elements over a significantly wider area of surface. Combined with the effects of water and the new 'channels' created for water to travel through, collect in, and contact with these chemicals, a situation is created where mass-scale contamination can occur.
Some examples of environmental problems associated with mining operations are:
- Tar Creek, an abandoned mining area in Picher, Oklahoma that is now an Environmental Protection Agency superfund site. Water in the mine has leaked through into local groundwater, contaminating it with metals such as lead and cadmium. [1]
- Scouriotissa, a copper mine in Cyprus that has been abandoned. Contaminated dust blows off this site.
- Berkeley Lake, an abandoned pit mine in Butte, Montana that has filled with water which is now acidic and poisonous.
Although such issues have been associated with some mining operations in the past, modern mining practices have improved significantly and are subject to close environmental scrutiny.
Mining industry
While exploration and mining can sometimes be conducted by individual entrepreneurs or small business, most modern-day mines are large enterprises requiring large amounts of capital to establish. Consequently, the industry is dominated by large, often multinational, mostly publicly-listed companies. See Category:Mining companies for a list.
Mine Planning Software
One of the most dramatic changes in the mining industry has been the role that sophisticated three dimensional 3-D mine planning software packages have had. Initially relatively simple tasks - like rendering graphic images of drill holes - meant that it became easier for surveyors, geologists, mine planners, mining engineers and other technical staff to manipulate and visualize data. However, in recent years the range of integrated mine planning tools have meant that massively complex models can be built to optimize the extraction and processing of mineral resources.
See also
- Acid mine drainage
- Coal mining
- Remediation
- Ore grade
- Office of Surface Mining- United States Mining Regulation Agency
References
- Tom Morrison. 1992. Hardrock Gold: A Miner's Tale (ISBN 0806124423)
- Geobacter Project: Gold mines may owe their origins to bacteria (in PDF format)
External links
- Western Mining History - mining in the American West.
Wikipedia-Article "Drilling"
Drilling is the process of using a drill bit in a drill to produce holes.
Drilling in metal
Under normal usage, swarf is carried up and away from the tip of the drill bit by the fluting. The continued production of chips from the cutting edges produces more chips which continue the movement of the chips outwards from the hole. This continues until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly or totally from the hole while drilling). Lubricants and coolants (i.e. cutting fluid) are sometimes used to ease this problem and to prolong the tools life by cooling and lubricating the tip and chip flow. Coolant is introduced via holes through the drill shank see gun drill bits.
Straight fluting is used for copper or brass, as this exhibits less tendency to "dig in" or grab the material. If a helical drill (twist drill) is used then the same effect can be achieved by stoning a small flat parallel with the axis of the drill bit.
For heavy feeds and comparatively deep holes oil-hole drills can be used, with a lubricant pumped to the drill head through a small hole in the bit and flowing out along the fluting. A conventional drill press arrangement can be used in oil well drilling, but is more commonly seen in automatic drilling machinery in which it is the workpiece that rotates rather than the drill bit.
Drilling in wood
Wood being softer than most metals, drilling in wood is considerably easier and faster than drilling in metal. Cutting fluids are not used or needed. The main issue in drilling wood is assuring clean entry and exit holes and preventing burning. Avoiding burning is a question of using sharp bits and the appropriate cutting speed. Drill bits can tear out chips of wood around the top and bottom of the hole and this is undesirable in fine woodworking applications.
Holes are easier to start in wood as the drill bit can be accurately positioned by pushing it into the wood and creating a dimple. The bit will thus have no tendency to wander. In metal working, an accurate position needs to be marked with a punch to avoid the bit wandering from the desired position of the hole.
The ubiquitous twist drill bits used in metalworking also work well in wood, but they tend to chip wood out at the entry and exit of the hole. In some cases, as in rough holes for carpentry, the quality of the hole does not matter, and a number of bits for fast cutting in wood exist, including spade bits and self-feeding auger bits. Many types of specialised drill bits for boring clean holes in wood have been developed, including brad-point bits, Forstner bits and hole saws.
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