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61-493: Smitham is the small lumps of ore which free miners scavenged because they were exempt from payment of lot and cope duties . This practice was brought to an end in 1760 when the Duke of Devonshire challenged the practice in chancery on the basis that mine owners were breaking larger lumps down to avoid taxation . Smitham rhymes with rhythm and together they are the only ɪðəm perfect rhymes. This article about mining

122-488: A crust , a mottled zone and a pallid zone. He cautions strongly against the concept of "lateritic deep weathering" since "it begs so many questions". Tropical weathering (laterization) is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The initial products of weathering are essentially kaolinized rocks called saprolites . A period of active laterization extended from about

183-458: A centimeter over several million years. The average diameter of a polymetallic nodule is between 3 and 10 cm (1 and 4 in) in diameter and are characterized by enrichment in iron, manganese, heavy metals , and rare earth element content when compared to the Earth's crust and surrounding sediment. The proposed mining of these nodules via remotely operated ocean floor trawling robots has raised

244-463: A complete weathering profile or theory about weathering), has led to calls for the term to be abandoned altogether. At least a few researchers, including T. R. Paton and M. A. J. Williams, specializing in regolith development have considered that hopeless confusion has evolved around the name. Material that looks highly similar to the Indian laterite occurs abundantly worldwide. Historically, laterite

305-493: A high clay content, which means they have higher cation exchange capacity , low permeability, high plasticity and high water-holding capacity than sandy soils. It is because the particles are so small, the water is trapped between them. After the rain, the water moves into the soil slowly. Due to intensive leaching, laterite soils lack in fertility in comparison to other soils, however they respond readily to manuring and irrigation. Palms are less likely to suffer from drought because

366-438: A major source of iron and aluminum ore. Percolating waters caused degradation of the parent basalt and preferential precipitation by acidic water through the lattice left the iron and aluminum ores. Primary olivine , plagioclase feldspar and augite were successively broken down and replaced by a mineral assemblage consisting of hematite , gibbsite , goethite , anatase , halloysite and kaolinite . Laterite ores were

427-544: A major source of iron and aluminum ores. Laterite ores also were the early major source of nickel . Francis Buchanan-Hamilton first described and named a laterite formation in southern India in 1807. He named it laterite from the Latin word later , which means a brick; this highly compacted and cemented soil can easily be cut into brick-shaped blocks for building. The word laterite has been used for variably cemented, sesquioxide -rich soil horizons . A sesquioxide

488-644: A number of ecological concerns. The extraction of ore deposits generally follows these steps. Progression from stages 1–3 will see a continuous disqualification of potential ore bodies as more information is obtained on their viability: With rates of ore discovery in a steady decline since the mid 20th century, it is thought that most surface level, easily accessible sources have been exhausted. This means progressively lower grade deposits must be turned to, and new methods of extraction must be developed. Some ores contain heavy metals , toxins, radioactive isotopes and other potentially negative compounds which may pose

549-413: A result of the precipitation of dissolved ore constituents out of fluids. Laterites form from the weathering of highly mafic rock near the equator. They can form in as little as one million years and are a source of iron (Fe), manganese (Mn), and aluminum (Al). They may also be a source of nickel and cobalt when the parent rock is enriched in these elements. Banded iron formations (BIFs) are

610-824: A risk to the environment or health. The exact effects an ore and its tailings have is dependent on the minerals present. Tailings of particular concern are those of older mines, as containment and remediation methods in the past were next to non-existent, leading to high levels of leaching into the surrounding environment. Mercury and arsenic are two ore related elements of particular concern. Additional elements found in ore which may have adverse health affects in organisms include iron, lead, uranium, zinc, silicon, titanium, sulfur, nitrogen, platinum, and chromium. Exposure to these elements may result in respiratory and cardiovascular problems and neurological issues. These are of particular danger to aquatic life if dissolved in water. Ores such as those of sulphide minerals may severely increase

671-552: A sizeable portion of international trade in raw materials both in value and volume. This is because the worldwide distribution of ores is unequal and dislocated from locations of peak demand and from smelting infrastructure. Most base metals (copper, lead, zinc, nickel) are traded internationally on the London Metal Exchange , with smaller stockpiles and metals exchanges monitored by the COMEX and NYMEX exchanges in

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732-466: A sudden global cooling. The rate of laterization would have decreased with the abrupt cooling of the earth. Weathering in tropical climates continues to this day, at a reduced rate. Laterites are formed from the leaching of parent sedimentary rocks ( sandstones , clays , limestones ); metamorphic rocks ( schists , gneisses , migmatites ); igneous rocks ( granites , basalts , gabbros , peridotites ); and mineralized proto-ores; which leaves

793-613: Is 45 to 60% Al 2 O 3 and 20 to 30% Fe 2 O 3 . The remaining weight consists of silicas (quartz, chalcedony and kaolinite ), carbonates ( calcite , magnesite and dolomite ), titanium dioxide and water. Bauxites of economical interest must be low in kaolinite. Formation of lateritic bauxites occurs worldwide in the 145- to 2-million-year-old Cretaceous and Tertiary coastal plains. The bauxites form elongate belts, sometimes hundreds of kilometers long, parallel to Lower Tertiary shorelines in India and South America; their distribution

854-446: Is a stub . You can help Misplaced Pages by expanding it . Ore Minerals of interest are generally oxides , sulfides , silicates , or native metals such as copper or gold . Ore bodies are formed by a variety of geological processes generally referred to as ore genesis and can be classified based on their deposit type. Ore is extracted from the earth through mining and treated or refined , often via smelting , to extract

915-404: Is a possible application of this low-cost, low-technology, visually unobtrusive, efficient system for rural areas with dispersed point sources of pollution. Ores are concentrated in metalliferous laterites; aluminum is found in bauxites , iron and manganese are found in iron-rich hard crusts, nickel and copper are found in disintegrated rocks, and gold is found in mottled clays. Bauxite ore

976-433: Is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land area containing laterites is between the tropics of Cancer and Capricorn . Laterite has commonly been referred to as a soil type as well as being a rock type. This, and further variation in the modes of conceptualizing about laterite (e.g. also as

1037-617: Is also widely used in Brazil for road building. Bedrock in tropical zones is often granite, gneiss, schist or sandstone; the thick laterite layer is porous and slightly permeable so the layer can function as an aquifer in rural areas. One example is the Southwestern Laterite (Cabook) Aquifer in Sri Lanka. This aquifer is on the southwest border of Sri Lanka, with the narrow Shallow Aquifers on Coastal Sands between it and

1098-747: Is an oxide with three atoms of oxygen and two metal atoms. It has also been used for any reddish soil at or near the Earth's surface. Laterite covers are thick in the stable areas of the Western Ethiopian Shield , on cratons of the South American Plate, and on the Australian Shield . In Madhya Pradesh , India, the laterite which caps the plateau is 30 m (100 ft) thick. Laterites can be either soft and easily broken into smaller pieces, or firm and physically resistant. Basement rocks are buried under

1159-425: Is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by intensive and prolonged weathering of the underlying parent rock , usually when there are conditions of high temperatures and heavy rainfall with alternate wet and dry periods. The process of formation is called laterization . Tropical weathering

1220-410: Is considered alluvial if formed via river, colluvial if by gravity, and eluvial when close to their parent rock. Polymetallic nodules , also called manganese nodules, are mineral concretions on the sea floor formed of concentric layers of iron and manganese hydroxides around a core. They are formed by a combination of diagenetic and sedimentary precipitation at the estimated rate of about

1281-412: Is known as gangue . The valuable ore minerals are separated from the gangue minerals by froth flotation , gravity concentration, electric or magnetic methods, and other operations known collectively as mineral processing or ore dressing . Mineral processing consists of first liberation, to free the ore from the gangue, and concentration to separate the desired mineral(s) from it. Once processed,

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1342-412: Is not related to a particular mineralogical composition of the parent rock. Many high-level bauxites are formed in coastal plains which were subsequently uplifted to their present altitude. The basaltic laterites of Northern Ireland were formed by extensive chemical weathering of basalts during a period of volcanic activity. They reach a maximum thickness of 30 m (100 ft) and once provided

1403-479: Is one occurrence of a particular ore type. Most ore deposits are named according to their location, or after a discoverer (e.g. the Kambalda nickel shoots are named after drillers), or after some whimsy, a historical figure, a prominent person, a city or town from which the owner came, something from mythology (such as the name of a god or goddess) or the code name of the resource company which found it (e.g. MKD-5

1464-498: Is the main source of aluminum. It is a variety of laterite (residual sedimentary rock), so it has no precise chemical formula. It is composed mainly of hydrated alumina minerals such as gibbsite [Al(OH) 3 or Al 2 O 3 . 3H 2 O)] in newer tropical deposits; in older subtropical, temperate deposits the major minerals are boehmite [γ-AlO(OH) or Al 2 O 3 .H 2 O] and some diaspore [α-AlO(OH) or Al 2 O 3 .H 2 O]. The average chemical composition of bauxite, by weight,

1525-514: The subsoils of the equatorial forests, of the savannas of the humid tropical regions, and of the Sahelian steppes . They cover most of the land area between the tropics of Cancer and Capricorn; areas not covered within these latitudes include the extreme western portion of South America, the southwestern portion of Africa, the desert regions of north-central Africa, the Arabian peninsula and

1586-582: The Angkor monuments—which are widely distributed in Cambodia and Thailand—between the 9th and 13th centuries. The stone materials used were sandstone and laterite; brick had been used in monuments constructed in the 9th and 10th centuries. Two types of laterite can be identified; both types consist of the minerals kaolinite, quartz, hematite and goethite. Differences in the amounts of minor elements arsenic, antimony, vanadium and strontium were measured between

1647-513: The Philippines. Laterites reflect past weathering conditions; laterites which are found in present-day non-tropical areas are products of former geological epochs , when that area was near the equator. Present-day laterite occurring outside the humid tropics are considered to be indicators of climatic change, continental drift or a combination of both. In India, laterite soils occupy an area of 240,000 square kilometres. Laterite soils have

1708-553: The Semi-Arid Tropics ( ICRISAT ) has employed this system to rehabilitate degraded laterite soils in Niger and increase smallholder farmers' incomes. In some places, these soils support grazing grounds and scrub forests. When moist, laterites can easily be cut with a spade into regular-sized blocks. Laterite is mined while it is below the water table, so it is wet and soft. Upon exposure to air it gradually hardens as

1769-516: The US and Japan. For detailed petrographic descriptions of ore minerals see Tables for the Determination of Common Opaque Minerals by Spry and Gedlinske (1987). Below are the major economic ore minerals and their deposits, grouped by primary elements. [REDACTED] Media related to Ores at Wikimedia Commons Laterite Laterite is a soil type rich in iron and aluminium and

1830-752: The United States and the Shanghai Futures Exchange in China. The global Chromium market is currently dominated by the United States and China. Iron ore is traded between customer and producer, though various benchmark prices are set quarterly between the major mining conglomerates and the major consumers, and this sets the stage for smaller participants. Other, lesser, commodities do not have international clearing houses and benchmark prices, with most prices negotiated between suppliers and customers one-on-one. This generally makes determining

1891-553: The acidity of their immediate surroundings and of water, with numerous, long lasting impacts on ecosystems. When water becomes contaminated it may transport these compounds far from the tailings site, greatly increasing the affected range. Uranium ores and those containing other radioactive elements may pose a significant threat if leaving occurs and isotope concentration increases above background levels. Radiation can have severe, long lasting environmental impacts and cause irreversible damage to living organisms. Metallurgy began with

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1952-418: The contrary, in the wetter parts of laterites subject to leaching ferricretes have been suggested to form. The mineralogical and chemical compositions of laterites are dependent on their parent rocks. Laterites consist mainly of quartz , zircon , and oxides of titanium , iron, tin , aluminum and manganese , which remain during the course of weathering. Quartz is the most abundant relic mineral from

2013-417: The direct working of native metals such as gold, lead and copper. Placer deposits, for example, would have been the first source of native gold. The first exploited ores were copper oxides such as malachite and azurite, over 7000 years ago at Çatalhöyük . These were the easiest to work, with relatively limited mining and basic requirements for smelting. It is believed they were once much more abundant on

2074-562: The earth which experienced prolonged tropical weathering of ultramafic rocks containing the ferro-magnesian minerals olivine , pyroxene , and amphibole . Yves Tardy, from the French Institut National Polytechnique de Toulouse and the Centre National de la Recherche Scientifique , calculated that laterites cover about one-third of the Earth's continental land area. Lateritic soils are

2135-583: The effectiveness of granular laterite in removing phosphorus and heavy metals from landfill leachate . Initial laboratory studies show that laterite is capable of 99% removal of phosphorus from solution. A pilot-scale experimental facility containing laterite achieved 96% removal of phosphorus. This removal is greater than reported in other systems. Initial removals of aluminum and iron by pilot-scale facilities have been up to 85% and 98% respectively. Percolating columns of laterite removed enough cadmium , chromium and lead to undetectable concentrations. There

2196-402: The gangue is known as tailings , which are useless but potentially harmful materials produced in great quantity, especially from lower grade deposits. An ore deposit is an economically significant accumulation of minerals within a host rock. This is distinct from a mineral resource in that it is a mineral deposit occurring in high enough concentration to be economically viable. An ore deposit

2257-458: The highest concentration of any single metal available. They are composed of chert beds alternating between high and low iron concentrations. Their deposition occurred early in Earth's history when the atmospheric composition was significantly different from today. Iron rich water is thought to have upwelled where it oxidized to Fe (III) in the presence of early photosynthetic plankton producing oxygen. This iron then precipitated out and deposited on

2318-675: The interior of Australia. Some of the oldest and most highly deformed ultramafic rocks which underwent laterization are found as petrified fossil soils in the complex Precambrian shields in Brazil and Australia. Smaller highly deformed Alpine-type intrusives have formed laterite profiles in Guatemala, Colombia, Central Europe, India and Burma. Large thrust sheets of Mesozoic island arcs and continental collision zones underwent laterization in New Caledonia, Cuba, Indonesian and

2379-450: The layers can function as aquifers in rural areas. Locally available laterites have been used in an acid solution, followed by precipitation to remove phosphorus and heavy metals at sewage-treatment facilities. Laterites are a source of aluminum ore ; the ore exists largely in clay minerals and the hydroxides , gibbsite , boehmite , and diaspore , which resembles the composition of bauxite . In Northern Ireland they once provided

2440-412: The leading source of copper ore. Porphyry copper deposits form along convergent boundaries and are thought to originate from the partial melting of subducted oceanic plates and subsequent concentration of Cu, driven by oxidation. These are large, round, disseminated deposits containing on average 0.8% copper by weight. Hydrothermal Hydrothermal deposits are a large source of ore. They form as

2501-404: The lowest to highest water table levels—is progressively depleted of the easily leached ions of sodium , potassium , calcium and magnesium . A solution of these ions can have the correct pH to preferentially dissolve silicon oxide rather than the aluminum oxides and iron oxides . Silcrete has been suggested to form in zones in relatively dry "precipitating zones" of laterites. To

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2562-626: The main tin source, began. Some 3000 years ago, the smelting of iron ores began in Mesopotamia . Iron oxide is quite abundant on the surface and forms from a variety of processes. Until the 18th century gold, copper, lead, iron, silver, tin, arsenic and mercury were the only metals mined and used. In recent decades, Rare Earth Elements have been increasingly exploited for various high-tech applications. This has led to an ever-growing search for REE ore and novel ways of extracting said elements. Ores (metals) are traded internationally and comprise

2623-502: The major source of early nickel. Rich laterite deposits in New Caledonia were mined starting the end of the 19th century to produce white metal . The discovery of sulfide deposits of Sudbury , Ontario, Canada, during the early part of the 20th century shifted the focus to sulfides for nickel extraction. About 70% of the Earth's land-based nickel resources are contained in laterites; they currently account for about 40% of

2684-472: The mid- Tertiary to the mid- Quaternary periods (35 to 1.5 million years ago). Statistical analyses show that the transition in the mean and variance levels of O during the middle of the Pleistocene was abrupt. It seems this abrupt change was global and mainly represents an increase in ice mass; at about the same time an abrupt decrease in sea surface temperatures occurred; these two changes indicate

2745-476: The mid-1980s, constructed trial sections of bituminous-surfaced low-volume roads using laterite in place of stone as a base course. The laterite did not conform with any accepted specifications but performed equally well when compared with adjoining sections of road using stone or other stabilized material as a base. In 1984 US$ 40,000 per 1 km (0.62 mi) was saved in Malawi by using laterite in this way. It

2806-675: The moisture between the flat clay particles evaporates and the larger iron salts lock into a rigid lattice structure and become resistant to atmospheric conditions. The art of quarrying laterite material into masonry is suspected to have been introduced from the Indian subcontinent. They harden like iron when they are exposed to air. After 1000 CE Angkorian construction changed from circular or irregular earthen walls to rectangular temple enclosures of laterite, brick and stone structures. Geographic surveys show areas which have laterite stone alignments which may be foundations of temple sites that have not survived. The Khmer people constructed

2867-479: The more insoluble ions, predominantly iron and aluminum. The mechanism of leaching involves acid dissolving the host mineral lattice , followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminum and silica under the high temperature conditions of a humid sub-tropical monsoon climate . An essential feature for the formation of laterite is the repetition of wet and dry seasons . Rocks are leached by percolating rain water during

2928-582: The ocean floor. The banding is thought to be a result of changing plankton population. Sediment Hosted Copper forms from the precipitation of a copper rich oxidized brine into sedimentary rocks. These are a source of copper primarily in the form of copper-sulfide minerals. Placer deposits are the result of weathering, transport, and subsequent concentration of a valuable mineral via water or wind. They are typically sources of gold (Au), platinum group elements (PGE), sulfide minerals , tin (Sn), tungsten (W), and rare-earth elements (REEs). A placer deposit

2989-404: The ocean. It has the considerable water-holding capacity, depending on the depth of the formation. The aquifer in this laterite recharges rapidly with the rains of April–May which follow the dry season of February–March, and continues to fill with the monsoon rains. The water table recedes slowly and is recharged several times during the rest of the year. In some high-density suburban areas

3050-409: The parent rock. Laterites vary significantly according to their location, climate and depth. The main host minerals for nickel and cobalt can be either iron oxides , clay minerals or manganese oxides . Iron oxides are derived from mafic igneous rocks and other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks. Nickel laterites occur in zones of

3111-431: The price of ores of this nature opaque and difficult. Such metals include lithium , niobium - tantalum , bismuth , antimony and rare earths . Most of these commodities are also dominated by one or two major suppliers with >60% of the world's reserves. China is currently leading in world production of Rare Earth Elements. The World Bank reports that China was the top importer of ores and metals in 2005 followed by

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3172-736: The rainwater is held in the soil. However, if the structure of lateritic soils becomes degraded, a hard crust can form on the surface, which hinders water infiltration, the emergence of seedlings, and leads to increased runoff. It is possible to rehabilitate such soils, using a system called the 'bio-reclamation of degraded lands'. This involves using indigenous water-harvesting methods (such as planting pits and trenches), applying animal and plant residues, and planting high-value fruit trees and indigenous vegetable crops that are tolerant of drought conditions. These soils are most suitable for plantation crops. They are good for oil palm, tea, coffee and cashew cultivation. The International Crops Research Institute for

3233-471: The surface than today. After this, copper sulphides would have been turned to as oxide resources depleted and the Bronze Age progressed. Lead production from galena smelting may have been occurring at this time as well. The smelting of arsenic-copper sulphides would have produced the first bronze alloys. The majority of bronze creation however required tin, and thus the exploitation of cassiterite,

3294-428: The temple contain laterite blocks behind the sandstone surface. The masonry was laid without joint mortar. It is used as a local building material in places such as Burkina Faso , where it is valued for being strong and for reducing heating and cooling costs. The French surfaced roads in the Cambodia, Thailand and Vietnam area with crushed laterite, stone or gravel. Kenya, during the mid-1970s, and Malawi, during

3355-528: The thick weathered layer and rarely exposed. Lateritic soils form the uppermost part of the laterite cover. In some places laterites contain pisolites and ferricrete , and they may be found in elevated positions as result of relief inversion . Cliff Ollier has criticized the usefulness of the concept given that it is used to mean different things to different authors. Reportedly some have used it for ferricrete, others for tropical red earth soil, and yet others for soil profiles made, from top to bottom, of

3416-545: The two laterites. Angkor Wat —located in present-day Cambodia—is the largest religious structure built by Suryavarman II , who ruled the Khmer Empire from 1112 to 1152. It is a World Heritage site. The sandstone used for the building of Angkor Wat is Mesozoic sandstone quarried in the Phnom Kulen Mountains, about 40 km (25 mi) away from the temple. The foundations and internal parts of

3477-457: The valuable metals or minerals. Some ores, depending on their composition, may pose threats to health or surrounding ecosystems. The word ore is of Anglo-Saxon origin, meaning lump of metal . In most cases, an ore does not consist entirely of a single mineral, but it is mixed with other valuable minerals and with unwanted or valueless rocks and minerals. The part of an ore that is not economically desirable and that cannot be avoided in mining

3538-702: The water table could recede to 15 m (50 ft) below ground level during a prolonged dry period of more than 65 days. The Cabook Aquifer laterites support relatively shallow aquifers that are accessible to dug wells. In Northern Ireland, phosphorus enrichment of lakes due to agriculture is a significant problem. Locally available laterite—a low-grade bauxite rich in iron and aluminum—is used in acid solution, followed by precipitation to remove phosphorus and heavy metals at several sewage treatment facilities. Calcium-, iron- and aluminum-rich solid media are recommended for phosphorus removal. A study, using both laboratory tests and pilot-scale constructed wetlands, reports

3599-463: The wet season; the resulting solution containing the leached ions is brought to the surface by capillary action during the dry season. These ions form soluble salt compounds which dry on the surface; these salts are washed away during the next wet season. Laterite formation is favored in low topographical reliefs of gentle crests and plateaus which prevents erosion of the surface cover. The reaction zone where rocks are in contact with water—from

3660-413: Was cut into brick-like shapes and used in monument-building. After 1000 CE, construction at Angkor Wat and other southeast Asian sites changed to rectangular temple enclosures made of laterite, brick, and stone. Since the mid-1970s, some trial sections of bituminous -surfaced, low-volume roads have used laterite in place of stone as a base course. Thick laterite layers are porous and slightly permeable, so

3721-472: Was the in-house name for the Mount Keith nickel sulphide deposit ). Ore deposits are classified according to various criteria developed via the study of economic geology, or ore genesis . The following is a general categorization of the main ore deposit types: Magmatic deposits are ones who originate directly from magma These are ore deposits which form as a direct result of metamorphism. These are

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