Mining is the extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, chalk, dimension stone, rock salt, potash, gravel, and clay. The ore must be a rock or mineral that contains valuable constituent, can be extracted or mined and sold for profit.[1] Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.
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 or restoration of the land after the mine is closed.[2] Mining materials are often obtained from ore bodies, lodes, veins, seams, reefs, or placer deposits. The exploitation of these deposits for raw materials is dependent on investment, labor, energy, refining, and transportation cost.
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Mining operations can 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; however, the outsized role of mining in generating business for often rural, remote or economically depressed communities means that governments often fail to fully enforce such regulations. Work safety has long been a concern as well, and where enforced, modern practices have significantly improved safety in mines. Unregulated or poorly regulated mining, especially in developing economies, frequently contributes to local human rights violations and environmental conflicts. Mining can also perpetuate political instability through resource conflicts.
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 mining maps.[11] The miners crushed the ore and ground it to a fine powder before washing the powder for the gold dust known as the dry and wet attachment processes.[12]
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 using a now-obsolete form of mining known as hushing. They built numerous aqueducts to supply water to the minehead, where the water was 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-bearing veins. The rock was then worked 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.
Sluicing methods were 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. The Romans also exploited the silver present in the argentiferous galena in the mines of Cartagena (Cartago Nova), Linares (Castulo), Plasenzuela and Azuaga, among many others.[16] 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,[17] 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. These were used extensively in the copper mines at Rio Tinto in Spain, where one sequence comprised 16 such wheels arranged in pairs, and lifting water about 24 metres (79 ft). 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.[18]
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. Medieval knights, for example, were often laden with up to 100 pounds (45 kg) of plate or chain link armour in addition to swords, lances and other weapons.[19] The overwhelming dependency on iron for military purposes spurred iron production and extraction processes.
The silver crisis of 1465 occurred when all mines had reached depths at which the shafts could no longer be pumped dry with the available technology.[20] Although an increased use of banknotes, credit and copper coins during this period did decrease the value of, and dependence on, precious metals, gold and silver still remained vital to the story of medieval mining.
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 1568 and a law in 1688. 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 1642 a colony of 4,000 foreigners was mining and smelting copper at Keswick in the northwestern mountains.[21]
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. Black powder was first used in mining in Selmecbnya, Kingdom of Hungary (now Bansk tiavnica, Slovakia) in 1627.[22] Black powder allowed blasting of rock and earth to loosen and reveal ore veins. Blasting was much faster than fire-setting and allowed the mining of previously impenetrable metals and ores.[23] In 1762, one of the world's first mining academies was established in the same town there.
Much of the knowledge of medieval mining techniques comes from books such as Biringuccio's De la pirotechnia and probably most importantly from Georg Agricola's De re metallica (1556). 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 mechanically- and animal-driven pumps.
Iron metallurgy in Africa dates back over four thousand years. Gold became an important commodity for Africa during the trans-Saharan gold trade from the 7th century to the 14th century. Gold was often traded to Mediterranean economies that demanded gold and could supply salt, even though much of Africa was abundant with salt due to the mines and resources in the Sahara desert. The trading of gold for salt was mostly used to promote trade between the different economies.[25] Since the Great Trek in the 19th century, after, gold and diamond mining in Southern Africa has had major political and economic impacts. The Democratic Republic of Congo is the largest producer of diamonds in Africa, with an estimated 12 million carats in 2019. Other types of mining reserves in Africa include cobalt, bauxite, iron ore, coal, and copper.[26]
Mining in the United States became widespread in the 19th century, and the United States Congress passed the General Mining Act of 1872 to encourage mining of federal lands.[35] As with the California Gold Rush in the mid-19th century, mining for minerals and precious metals, along with ranching, became a driving factor in the U.S. Westward Expansion to the Pacific coast. With the exploration of the West, mining camps sprang up 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.[36] Aided by railroads, many people traveled West for work opportunities in mining. Western cities such as Denver and Sacramento originated as mining towns.[37] 17dc91bb1f
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