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Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an orebody , lode , vein , seam , reef or placer deposit. These deposits form a mineralized package that is of economic 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 through agricultural processes, or created artificially in a laboratory or factory.
Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water. Mining of stones and metal has been a human activity since pre-historic times.
Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed. Mining operations usually create a negative environmental impact, both during the mining activity and after the mine has closed. Hence, most of the world's nations have passed regulations to decrease the impact. Work safety has long been a concern as well, and modern practices have significantly improved safety in mines.
Levels of metals recycling are generally low. Unless future end-of-life recycling rates are stepped up, some rare metals may become unavailable for use in a variety of consumer products.
Due to the low recycling rates, some landfills now contain higher concentrations of metal than mines themselves. 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 early tools and weapons ; for example, high quality flint found in northern France , southern England and Poland was used to create flint tools. The mines at Grimes Graves and Krzemionki are especially famous, and like most other flint mines, are Neolithic in origin ca — BC.
Other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District. The oldest-known mine on archaeological record is the Ngwenya Mine in Swaziland , which radiocarbon dating shows to be about 43, years old.
At this site Paleolithic humans mined hematite to make the red pigment ochre. Ancient Egyptians mined malachite at Maadi. Later, between and BC, large building projects required expeditions abroad to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself.
Mining in Egypt occurred in the earliest dynasties. The gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. These mines are described by the Greek author Diodorus Siculus , who mentions fire-setting as one method used to break down the hard rock holding the gold.
One of the complexes is shown in one of the earliest known maps. The miners crushed the ore and ground it to a fine powder before washing the powder for the gold dust.
Mining in Europe has a very long history. Examples include the silver mines of Laurium , which helped support the Greek city state of Athens. Although they had over 20, slaves working them, their technology was essentially identical to their Bronze Age predecessors.
However, it was the Romans who developed large scale mining methods, especially the use of large volumes of water brought to the minehead by numerous aqueducts. The water was used for a variety of purposes, including removing overburden and rock debris, called hydraulic mining , as well as washing comminuted , or crushed, ores and driving simple machinery. The Romans used hydraulic mining methods on a large scale to prospect for the veins of ore, especially a now-obsolete form of mining known as hushing.
They built numerous aqueducts to supply water to the minehead. There, the water stored in large reservoirs and tanks. When a full tank was opened, the flood of water sluiced away the overburden to expose the bedrock underneath and any gold veins.
The rock was then worked upon by fire-setting to heat the rock, which would be quenched with a stream of water. The resulting thermal shock cracked the rock, enabling it to be removed by further streams of water from the overhead tanks. The Roman miners used similar methods to work cassiterite deposits in Cornwall and lead ore in the Pennines.
The methods had been developed by the Romans in Spain in 25 AD to exploit large alluvial gold deposits, the largest site being at Las Medulas , where seven long aqueducts tapped local rivers and sluiced the deposits. Spain was one of the most important mining regions, but all regions of the Roman Empire were exploited. In Great Britain the natives had mined minerals for millennia , [11] but after the Roman conquest , the scale of the operations increased dramatically, as the Romans needed Britannia 's resources, especially gold , silver , tin , and lead.
Roman techniques were not limited to surface mining. They followed the ore veins underground once opencast mining was no longer feasible. At Dolaucothi they stoped out the veins and drove adits through bare rock to drain the stopes.
The same adits were also used to ventilate the workings, especially important when fire-setting was used. At other parts of the site, they penetrated the water table and dewatered the mines using several kinds of machines, especially reverse overshot water-wheels. They were worked as treadmills with miners standing on the top slats. Many examples of such devices have been found in old Roman mines and some examples are now preserved in the British Museum and the National Museum of Wales.
Mining as an industry underwent dramatic changes in medieval Europe. The mining industry in the early Middle Ages was mainly focused on the extraction of copper and iron. Other precious metals were also used, mainly for gilding or coinage. Initially, many metals were obtained through open-pit mining , and ore was primarily extracted from shallow depths, rather than through deep mine shafts.
Around the 14th century, the growing use of weapons, armour, stirrups , and horseshoes greatly increased the demand for iron. The silver crisis of occurred when all mines had reached depths at which the shafts could no longer be pumped dry with the available technology.
Due to differences in the social structure of society, the increasing extraction of mineral deposits spread from central Europe to England in the mid-sixteenth century.
On the continent, mineral deposits belonged to the crown, and this regalian right was stoutly maintained. But in England, royal mining rights were restricted to gold and silver of which England had virtually no deposits by a judicial decision of and a law in England had iron, zinc, copper, lead, and tin ores.
Landlords who owned the base metals and coal under their estates then had a strong inducement to extract these metals or to lease the deposits and collect royalties from mine operators.
English, German, and Dutch capital combined to finance extraction and refining. Hundreds of German technicians and skilled workers were brought over; in a colony of 4, foreigners was mining and smelting copper at Keswick in the northwestern mountains. Use of water power in the form of water mills was extensive.
The water mills were employed in crushing ore, raising ore from shafts, and ventilating galleries by powering giant bellows. Blasting was much faster than fire-setting and allowed the mining of previously impenetrable metals and ores.
The widespread adoption of agricultural innovations such as the iron plowshare , as well as the growing use of metal as a building material, was also a driving force in the tremendous growth of the iron industry during this period.
Inventions like the arrastra were often used by the Spanish to pulverize ore after being mined. This device was powered by animals and used the same principles used for grain threshing. These books detail many different mining methods used in German and Saxon mines. A prime issue in medieval mines, which Agricola explains in detail, was the removal of water from mining shafts. As miners dug deeper to access new veins, flooding became a very real obstacle.
The mining industry became dramatically more efficient and prosperous with the invention of mechanical and animal driven pumps. Mining in the Philippines began around BC. The early Filipinos worked various mines of gold, silver, copper and iron. Jewels, gold ingots, chains, calombigas and earrings were handed down from antiquity and inherited from their ancestors.
Gold dagger handles, gold dishes, tooth plating, and huge gold ornamets were also used. Some outstanding examples of Philippine jewelry included necklaces, belts, armlets and rings placed around the waist. There are ancient, prehistoric copper mines along Lake Superior , and metallic copper was still found there, near the surface, in colonial times.
Indigenous peoples availed themselves of this copper starting at least 5, years ago," [20] and copper tools, arrowheads, and other artifacts that were part of an extensive native trade network have been discovered. In addition, obsidian , flint , and other minerals were mined, worked, and traded.
In the early colonial history of the Americas, "native gold and silver was quickly expropriated and sent back to Spain in fleets of gold- and silver-laden galleons," [23] the gold and silver originating mostly from mines in Central and South America. Chalchihuitl using stone tools before Mining in the United States became prevalent in the 19th century, and the General Mining Act of was passed to encourage mining of federal lands.
With the exploration of the West, mining camps were established and "expressed a distinctive spirit, an enduring legacy to the new nation;" Gold Rushers would experience the same problems as the Land Rushers of the transient West that preceded them.
Western cities such as Denver and Sacramento originated as mining towns. When new areas were explored, it was usually the gold placer and then lode and then silver that were taken into possession and extracted first. Other metals would often wait for railroads or canals, as coarse gold dust and nuggets do not require smelting and are easy to identify and transport.
In the early 20th century, the gold and silver rush to the western United States also stimulated mining for coal as well as base metals such as copper, lead, and iron. Areas in modern Montana, Utah, Arizona, and later Alaska became predominate suppliers of copper to the world, which was increasingly demanding copper for electrical and households goods.
After declines in production, another boom in mining occurred in the s. Now, in the early 21st century, Australia remains a major world mineral producer. As the 21st century begins, a globalized mining industry of large multinational corporations has arisen. Peak minerals and environmental impacts have also become a concern.
Different elements, particularly rare earth minerals , have begun to increase in demand as a result of new technologies. The process of mining from discovery of an ore body through extraction of minerals and finally to returning the land to its natural state consists of several distinct steps. The first is discovery of the ore body, which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body. This leads to a mathematical resource estimation to estimate the size and grade of the deposit.
This estimation is used to conduct a pre-feasibility study to determine the theoretical economics of the ore deposit. This identifies, early on, whether further investment in estimation and engineering studies is warranted and identifies key risks and areas for further work.
The next step is to conduct a feasibility study to evaluate the financial viability, the technical and financial risks, and the robustness of the project.