Can you mine clay?
Terra Cotta, California
Coal, along with clay deposits, was found on the site by John D. Huff in the late 1880s, and the Southern California Coal and Clay Company was formed to mine them. The town site of Terra Cotta was laid out and was given a post office on October 26, 1887. In May 1893 its post office was closed and moved to Lake Elsinore. A plant for the manufacture of sewer and water pipes was built using the coal to fire ceramic pipes in the four kilns. The finished product had to be shipped by wagon six miles through Lake Elsinore to the La Laguna rail station at the mouth of Railroad Canyon until 1896 when a spur line was built through Lake Elsinore and Terra Cotta to the new clay deposits in Alberhill. The coal mined was also used locally as fuel for the stamping mill at the Good Hope Mine and was shipped elsewhere in the state.
Mining in Cornwall and Devon
During the 20th century various ores were briefly profitable, and mines were reopened, but today none remain. Dolcoath mine (Cornish for "Old Ground"), the 'Queen of Cornish Mines', was 3500 feet (1067 m) deep, and was for many years the deepest mine in the world, not to mention one of the oldest before its closure in 1921. Indeed, the last working tin mine in Europe was South Crofty, near Camborne, until its closure in March 1998. After an attempt was made to reopen it, it was abandoned. There were local media reports in September 2006 that South Crofty was being considered for re-opening as the price of tin had soared, but the site was subject to a Compulsory Purchase Order (October 2006). On the wall outside the gate is some graffiti dating from 1999:
Earth structure
Clays typically are phyllosilicate minerals with a sheet-like structure.
The very small clay particles interact with each other physically and chemically. 
Even a small proportion of clay affects the physical properties of the soil much more than might be expected.
Clays such as kaolinite do not expand or contract when wetted or dried, and are useful for brick-making. 
Others, such as smectites, expand or contract considerably when wet or dry, and are not suitable for building.
Metal clay
Metal clay artists looking for more strength in their silver creations can also mix PMC fine silver clay with an equal part of PMC Sterling clay. The firing of this alloy is found to be up to for two hours.
Mining industry of Angola
Angola is also rich in several other mineral resources that had not been fully exploited by the early twenty- first century . These include manganese, copper, gold, phosphates, granite, marble, uranium, quartz, lead, zinc, wolfram, tin, fluorite, sulfur, feldspar, kaolin, mica, asphalt, gypsum, and talc. The government hopes to resume mining in the southwest for crystalline quartz and ornamental marble. It has been estimated that 5,000 cubic meters of marble could be extracted annually for a period of twenty years. A state-owned company mined granite and marble in Huíla and Namibe Provinces, and in 1983 it produced 4,450 cubic meters of granite and 500 cubic meters of marble. Since then, the company has ceased production in order to re-tool with modern machinery. Quartz production, however, was suspended indefinitely because of the military situation in areas near the extraction sites in Cuanza Sul Province.
Quick clay
Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is any of several distinctively sensitive glaciomarine clays found in Canada, Norway, Russia, Sweden, Finland, the United States and other locations around the world. The clay is so unstable that when a mass of quick clay is subjected to sufficient stress, the material behavior may change from that of a particulate material to that of a fluid.
Mining
Surface mining is done by removing (stripping) surface vegetation, dirt, and, if necessary, 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, commonly associated with coal mining, which involves taking the top of a mountain off to reach ore deposits at depth. Most (but not all) placer deposits, because of their shallowly buried nature, are mined by surface methods. 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
Brickworks
In a large industrial brickworks, clay is taken from the quarry, and then carried by conveyor belt or truck/lorry to the main factory, although it may be stockpiled outside before entering the machinery. When the clay enters the preparation plant (Clay Prep) it is crushed, and mixed with water and other additives which may include breeze, a very fine anthracite that aids firing. This process, which is also known as pugmilling, improves the consistency, firing qualities, texture, and colour of the brick. From here, the processed clay can be extruded into a continuous strip and cut with wires, or put into moulds or presses (also referred to as "forming") to form the clay into its final shape. 
After the forming or cutting, the bricks must be dried, either in the open air, in drying sheds, or in special drying kilns. When the bricks have been dried, they must then be fired or 'burnt' in a kiln, to give them their final hardness and appearance.
The brick manufacturing process was revolutionised in the mid nineteenth century with the development of automated brickmaking machines such as the Bradley & Craven Ltd ‘Stiff-Plastic Brickmaking Machine’.
Flint mining
Flint has been mined since the Palaeolithic, but was most common during the Neolithic. Flint was especially valued in prehistory for its use in weaponry. Although flint is not as valuable a resource in modern times, a few flint mines remain in operation even today (for example at Miorcani).The above-mentioned flint mining sites and others are mentioned in the following texts:
Clay
Clays exhibit plasticity when mixed with water in certain proportions. However, when dry, clay becomes firm and when fired in a kiln, permanent physical and chemical changes occur. These changes convert the clay into a ceramic material. Because of these properties, clay is used for making pottery, both utilitarian and decorative, and construction products, such as bricks, wall and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered the useful properties of clay. Some of the earliest pottery shards recovered are from central Honshu, Japan. They are associated with the Jōmon culture and deposits they were recovered from have been dated to around 14,000 BC.
Shale
Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and water. These released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor (except quartz) minerals found in shales and other mudrocks.
Sand casting
The choice of sand has a lot to do with the temperature at which the metal is poured. At the temperatures that copper and iron are poured, the clay gets inactivated by the heat, in that the montmorillonite is converted to illite, which is a non-expanding clay. Most foundries do not have the very expensive equipment to remove the burned out clay and substitute new clay, so instead, those that pour iron typically work with silica sand that is inexpensive compared to the other sands. As the clay is burned out, newly mixed sand is added and some of the old sand is discarded or recycled into other uses. Silica is the least desirable of the sands, since metamorphic grains of silica sand have a tendency to explode to form sub-micron sized particles when thermally shocked during pouring of the molds. These particles enter the air of the work area and can lead to silicosis in the workers. Iron foundries spend a considerable effort on aggressive dust collection to capture this fine silica. The sand also has the dimensional instability associated with the conversion of quartz from alpha quartz to beta quartz at 680 °C (1250 °F). Often, combustible additives such as wood flour are added to create spaces for the grains to expand without deforming the mold. Olivine, chromite, etc. are therefore used because they do not have a phase transition that causes rapid expansion of the grains, as well as offering greater density, which cools the metal faster, producing finer grain structures in the metal. Since they are not metamorphic minerals, they do not have the polycrystals found in silica, and subsequently do not form hazardous sub-micron sized particles.
Slate industry
The slate industry is the industry related to the extraction and processing of slate. Slate is either quarried from a "slate quarry" or reached by tunneling in a "slate mine". Common uses for slate include as a roofing material, a flooring material, gravestones and memorial tablets, and for electrical insulation. Slate mines are found around the world and the major slate mining region in the United Kingdom is Wales: in Cornwall there are a number of slate quarries (famously the village of Delabole) and in the Lake District there are numerous slate mines and quarries.
Medicinal clay
Clays contain large amounts of trace minerals. It is common to see as many as 75 different trace minerals in Montmorillonite clays. Specific trace minerals that various clays possess vary very widely. Also, the amount of any particular trace mineral in any specific clay varies a lot among clays from different locations. For example, the amount of iron in various bentonite clays can vary from well below 1%, and up to 10%.
Stan Bitters
In his book "Environmental Ceramics", Bitters says that “Clay assumes powerful form in sculpture. Because of its responsive nature and its receptivity to impressions, clay is open to tremendous variety of sculptural approaches, and can be worked additively and subtractively with equal ease. Its visual mass gives it an earthy, weighty character in contrast to the liquid nature of glass or the linear character of welded steel in which a massive piece may appear to be much lighter than it is. The immediacy with which clay can be worked gives the sculpture great energy. Clay accepts and emits emotional power” (Bitters 1976, p. 77).
Tailings
The extraction of minerals from ore can be done two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires comminution, i.e., grinding the ore into fine particles to facilitate extraction of the target element(s). Because of this comminution, tailings consist of a slurry of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are usually produced from the mill in slurry form, which is a mixture of fine mineral particles and water.
Metal clay
Metal clay is a crafting medium consisting of very small particles of metal such as silver, gold, bronze, or copper mixed with an organic binder and water for use in making jewelry, beads and small sculptures. Originating in Japan in 1990, metal clay can be shaped just like any soft clay, by hand or using molds. After drying, the clay can be fired in a variety of ways such as in a kiln, with a handheld gas torch, or on a gas stove, depending on the type of clay and the metal in it. The binder burns away, leaving the pure sintered metal. Shrinkage of between 8% and 30% occurs (depending on the product used). Alloys such as bronze, sterling silver, and steel also are available.
Clay pit
A clay pit is a quarry or mine for the extraction of clay, which is generally used for manufacturing pottery, bricks or Portland cement. Quarries where clay is mined to make bricks are sometimes called brick pits.
Mudrock
A claystone is lithified, and non-fissile mudrock. In order for a rock to be considered a claystone, it must consist of up to fifty percent clay, which measures less than 1/256 of a millimeter in particle size. Clay minerals are integral to mudrocks, and represent the first or second most abundant constituent by volume. There are 35 recognized clay mineral species on Earth. They make muds cohesive and plastic, or able to flow. Clay is by far the smallest particles recognized in mudrocks. Most materials in nature are clay minerals, but quartz, feldspar, iron oxides, and carbonates can weather to sizes of a typical clay mineral.
Medicinal clay
Clay gathered from its original source deposit is refined and processed in various ways by manufacturers. This can include heating or baking the clay, since the raw clay tends to contain a variety of micro-organisms.
Winsford
Cornish china clay was used in the production of earthenware and stoneware. The clay was taken overland from Winsford by pack horse to manufacturers in the Potteries, a distance of about . Locally produced salt was also transported to the Potteries, for use in the manufacture of salt-glazed stoneware. Finished ceramics from the Potteries were brought back to Winsford, for export through the Port of Liverpool. That trade ended in the 1780s when the Trent and Mersey Canal opened and carried the goods through Middlewich, bypassing Winsford.
Geology of Cornwall
Extraction of tin began in Cornwall in prehistoric times and continued until the late 20th century. Historically extensive tin and copper mining has occurred in Devon and Cornwall, as well as arsenic, silver, zinc and a few other metals. Granite, slate and aggregate are still quarried and china-clay extraction continues on a large scale. 
There are ample supplies of granite worth the cost of shipping out of the county and much Cornish granite has been used in distant places. It is one of the most appropriate materials for memorials and examples are found in most parts of Cornwall. there are no active metalliferous mines remaining. However, tin deposits still exist in Cornwall, and there is talk of reopening South Crofty tin mine.
Metal clay
Metal clay first came out in Japan in 1990 to allow craft jewelry makers to make sophisticated looking jewelry without the years of study needed to make fine jewelry.
Clastic rock
According to Blatt, Middleton and Murray mudrocks that are composed mainly of silt particles are classified as siltstones. In turn, rocks that possess clay as the majority particle are called claystones. In geology, a mixture of both silt and clay is called mud. Rocks that possess large amounts of both clay and silt are called mudstones. In some cases the term shale is also used to refer to mudrocks and is still widely accepted by most. However, others have used the term shale to further divide mudrocks based on the percentage of clay constituents. The plate-like shape of clay allows its particles to stack up one on top of another creating laminae or beds. The more clay present in a given specimen, the more laminated a rock is. Shale, in this case, is reserved for mudrocks that are laminated, while mudstone refers those that are not.
Clay court
Natural clay courts are rare because this type of surface does not absorb water easily and takes two to three days to dry. A good example of natural red clay can be seen at the Frick Park Clay Courts in Pittsburgh, a public facility of six red clay courts that has been in continual use since 1930.
Ancient Egyptian pottery
The marl clay (or 'desert clay') is found along the Nile valley, from Esna to Cairo, in the Oases and at the edges of the Nile Delta. It is a yellow-white stone, which is found in limestone deposits. The deposits were created in the Pleistocene, when the original Nile river and its tributaries deposited this clay in what had previously been desert. Marl clay includes a range of kinds of clay based on their base substance. In general, they have a lower percentage of silicum and significantly higher calcium content. The most important sub-types of marl clay are:Marl clay is normally cream or white in colour when it is fired in an oxygen-rich oven. Cuts can reveal pink or orange areas. It is rich in mineral salts, so the outer surface often has a thin layer of weathered salt which forms a white surface layer when fired, which can be mistake for a 'glaze' by the unwary. At higher firing temperature (c. 1000 °C), this layer becomes olive-green and resembles a green glaze.
Medicinal clay
A wide variety of clays are used for medicinal purposes—primarily for external applications, such as the clay baths in health spas (mud therapy). Among the clays most commonly used are kaolin and the smectite clays such as bentonite, montmorillonite, and Fuller's earth.
Underground mining (hard rock)
Underground hard rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals such as ore containing gold, silver, iron, copper, zinc, nickel, tin and lead, but also involves using the same techniques for excavating ores of gems such as diamonds or rubies. Soft rock mining refers to excavation of softer minerals such as salt, coal, or oil sands.
Soil
Typically there are four main groups of clay minerals: kaolinite, montmorillonite-smectite, illite, and chlorite. Most clays are crystalline and most are made up of three or four planes of oxygen held together by planes of aluminium and silicon by way of ionic bonds that together form a single layer of clay. The spatial arrangement of the oxygen atoms determines clay's structure. Half of the weight of clay is oxygen, but on a volume basis oxygen is ninety percent. The layers of clay are sometimes held together through hydrogen bonds, sodium or potassium bridges and as a result will swell less in the presence of water. Clays such as montmorillonite have layers that are loosely attached and will swell greatly when water intervenes between the layers.
Japanese pottery and porcelain
Clay is chosen largely based on local materials available. There is an abundance of most basic types of clay in Japan. Due to naturally occurring kaolin deposits, many porcelain clays are found in Kyushu. Kilns were traditionally built at the sites of clay deposits, and most potters still use local clays, having developed a range of glazes and decoration techniques especially suited to that clay. The pottery clays found in the Japanese archipelago range from fusible earthenwares to refractory kaolins. From the Jōmon period to the Yayoi period, Japanese potters relied on high plastic iron-bearing shale and alluvial clays. Organic materials appear in much of the early Jōmon period work, but sand or crushed stone predominates thereafter. Further refinements came about under the Chinese influence in the 8th and 9th centuries AD, when creators of Nara three-color wares and Heian ash glazed wares sought out white, refractory clays and enhanced their fineness through levigation. In Kyoto, where demand makes it both practical and profitable, the clay is crushed, blunged (made into slip), and filtered commercially. To use the clay, you must first break it up into small pieces, pour a small amount of water over it, and beat it with a "kine", a wooden mallet, until you obtain the plasticity and uniformity of texture you want. Then you put it through an "aramomi" or "rough wedging" process, a kneading movement, after which the clay is stored for two or three days, or sometimes up to a week. Before the clay is ready to be thrown, it must pass through the "nejimomi" ("screw-wedge") process, which produces a bullet-shaped mass from which all air bubbles have been removed and in which the granular structure is arranged so that it radiates outwards from the center of the mass.
Fire clay
Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick. The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (AlO·2SiO·2HO) with or without free silica."
Aldridge
In the 1800s, Aldridge became an industrial town with coal mines and lime kilns. The coal and clay in the area prompted many to set up collieries and brickworks. Aldridge clay is especially useful in the manufacture of blue bricks. The 1881 census shows that the mines and brickworks were major employers. Because the coal and clay beneath the eastern side of Aldridge (towards Stonnall) is located much deeper under the surface, extraction of this coal and clay would not have been economically viable. As a result, farms continued to dominate the eastern part, though a sand quarry was set up and still remains on Birch Lane.
Rixton Clay Pits
Rixton Clay Pits (also known as Rixton Claypits) is a former clay extraction site in Rixton, near Hollins Green, Warrington, England. Formerly farmland, boulder clay extraction started in the 1920s for brick making in the adjacent brickworks, and ceased in 1965 - since when it has been allowed to return to nature. It is now an area of ponds, scrub, woodland and damp grassland. It is owned and managed by Warrington Borough Council as a local amenity.
Wealden iron industry
Iron ore in the form of siderite, commonly known as iron stone or historically as mine, occurs in patches or bands in the Cretaceous clays of the Weald. Differing qualities of ore were extracted and mixed by experienced smelters to give the best results. Sites of opencast quarries survive from the pre-Roman and Roman eras, but medieval ore extraction was mainly done by digging a series of minepits about five metres in diameter and up to twelve metres deep with material being winched up in baskets suspended from a wooden tripod. This was less destructive of the land as spoil from one pit was used to backfill the previous pit allowing continued land use.
Cliff mine
The Cliff mined a fissure vein of native copper in Precambrian conglomerate and basalt beds. The vein was nearly vertical, dipping steeply to the east, and running north-south, nearly perpendicular to the strike of the enclosing beds. The productive part of the vein was below the Greenstone flow, which forms the cliff from which the mine took its name. The mine started by mining only high-grade ore; in 1848, the average grade mined was 26% copper. The average ore grade mined declined over time, and by 1869 was 3% copper, comparable to other copper mines of the time. Some native silver was also recovered; approximately 41,000 ounces total silver was reported recovered in the years 1846-1852 and 1858-1871.
Brine mining
Commercial brines include both surface water (seawater and saline lakes) and groundwater (shallow brine beneath saline or dry lakes, and deep brines in sedimentary basins). Brine brought to the surface by geothermal energy wells often contains high concentrations of minerals, but is not currently used for commercial mineral extraction.
Metal clay
PMC was developed in the early 1990s in Japan by metallurgist Masaki Morikawa. As a solid-phase sintered product of a precious metal powder used to form a precious metal article, the material consists of microscopic particles of pure silver or fine gold and a water-soluble, non-toxic, organic binder that burns off during firing. Success was first achieved with gold and later duplicated with silver. 
The PMC brand includes the following products:
London Clay
Due to its impermeability especially when exposed by ploughing, London clay does not make good agricultural soil. In Middlesex, ploughing London Clay land so deep that it brings up clay has historically been called "ploughing up poison".
Minestone
Minestone, also known as colliery spoil, is the solid residual material resulting from the mining of coal. It is likely to contain varying proportions of sandstone, shale, mudstone and coal fragments. The properties of colliery spoil can vary considerably both within a tip and from tip to tip.
Ub, Serbia
The following table gives a preview of total number of employed people per their core activity (as of 2016):
There are several mines and resource centers of coal (Radljevo field - 344,000,000 tones, Zvizdar field - 280,000,000 tones), clay, sand, stone and limestone.
The biggest producer of quartz sand in Serbia is "Kopovi a.d.", with overall production of over 400,000 tones per year. 
Clay pits are based below the layers of sand and quartz sand. Municipality of Ub is the biggest supplier of high-quality clay in Serbia. There are more than 1,800,000 tones of clay.
Soil mechanics
The common clay minerals are montmorillonite or smectite, illite, and kaolinite or kaolin. These minerals tend to form in sheet or plate like structures, with length typically ranging between 10 m and 4x10 m and thickness typically ranging between 10 m and 2x10 m, and they have a relatively large specific surface area. The specific surface area (SSA) is defined as the ratio of the surface area of particles to the mass of the particles. Clay minerals typically have specific surface areas in the range of 10 to 1,000 square meters per gram of solid. Due to the large surface area available for chemical, electrostatic, and van der Waals interaction, the mechanical behavior of clay minerals is very sensitive to the amount of pore fluid available and the type and amount of dissolved ions in the pore fluid. To anticipate the effect of clay on the way a soil will behave, it is necessary to know the kinds of clays as well as the amount present. As home builders and highway engineers know all too well, soils containing certain high-activity clays make very unstable material on which to build because they swell when wet and shrink when dry. This shrink-and-swell action can easily crack foundations and cause retaining walls to collapse. These clays also become extremely sticky and difficult to work with when they are wet. In contrast, low-activity clays, formed under different conditions, can be very stable and easy to work with.
Chill (casting)
Chills can be made of many materials, including iron, copper, bronze, aluminium, graphite, and silicon carbide. Other sand materials with higher densities, thermal conductivity or thermal capacity can also be used as a chill. For example, chromite sand or zircon sand can be used when molding with silica sand.
Ball clay
Ball clays are kaolinitic sedimentary clays that commonly consist of 20–80% kaolinite, 10–25% mica, 6–65% quartz. Localized seams in the same deposit have variations in composition, including the quantity of the major minerals, accessory minerals and carbonaceous materials such as lignite. They are fine-grained and plastic in nature, and, unlike most earthenware clays, produce a fine quality white-coloured pottery body when fired, which is the key to their popularity with potters.
Afon Clun
Lead mines were opened in Mwyndy (between Llantrisant and Groesfaen) in the "Parke of Cloune" in May 1531 CE. By August 1531 iron ore was being mined there. Iron smelting began nearby during the summer of 1532, with one bloomery furnace site at Mwyndy, and (probably) another smaller smelting site at Rhiwsaeson, employing 4 blowers/hewars, with three blowers operating the bellows at any one time. They produced up to two blooms, of 50 kg per bloom per day, from 150 kg of ore, taking 6 to 7 hours each to produce. Charcoal to heat the furnaces was probably derived locally, from "Cloune Park" — mention is made by Rice Lewis in his 'A breviat of Glamorgan' (1595 and 1600) of the destruction of the forests of Garth Maelog and Allt Griffith because of the ironworks. The iron mines were leased by the crown in 1539, granting rights to mine and make iron and to build water powered ironworks within three miles of Cloune Park for 21 years. There is no evidence to suggest that either iron mining or smelting continued in the area after the 16th century.
Marine clay
Marine clay is a type of clay found in coastal regions around the world. In the northern, deglaciated regions, it can sometimes be quick clay, which is notorious for being involved in landslides.
Clay mineral X-ray diffraction
Clay minerals are one of the most diverse minerals but all have a commonalty of crystal or grain sizes below 2 µm. Chemically clays are defined by crystal structure and chemical composition. Sometimes fine grain sediments are mistakenly described as clays, this is actually a description of the “clay-size fraction” rather than the mineralogy of the sediment. There are three crystallographic clay groups: platy clays (phyllosilicates), fibrous clay minerals, and amorphous clay. Phyllosilicates are the most abundant clays and are categorized based on the layering of a tetrahedral and an octahedral layer. For most clays, the octahedral layer is centered with Al, Fe, or Mg(OH), but sometimes Zn, Li, and Cr can substitute as well. Si is normally the center of the tetrahedral layer but Al will often partially substitute and create a charge imbalance. Two-layer clays are composed of a tetrahedral layer and an octahedral layer (T-O) while three-layer clays contain an octahedral layer sandwiched by two tetrahedral layers (T-O-T). When substitution of Al for Si creates a charge imbalance, an interlayer cation will fill in between tetrahedral layers to balance the charge of the clay.
Fire clay
Unlike conventional brick-making clay, some fire clays (especially flint clays) are mined at depth, found as a seatearth, the underclay associated with coal measures.
Modelling clay
Ceramic clays are water-based substances made from clay minerals and other raw materials. They are baked at high temperatures in a process known as firing to create ceramics, such as terra cotta, earthenware, stoneware, and porcelain. Paper clay produced by pottery clay manufacturers is a clay body to which a small percentage of processed cellulose fiber has been added. When kiln-fired, the paper burns out, leaving the clay body. Consequently, the firing temperatures and glazes selection should be the same on those used with the clay body.
Cleveland-Cliffs Inc.
Demand for American iron ore hit peaks during World War I, World War II, and the post-WWII consumer boom. In 1933, Edward Greene (the son-in-law of Jeptha Homer Wade II) replaced William G. Mather as the head of the company. The Mather A Mine opened in the early 1940s and the Mather B shaft in the 1950s. As the Cold War continued, reserves of mineable hematite dwindled in northern Minnesota and Cleveland-Cliffs returned some of its focus to its traditional areas of interest around Marquette, Michigan, where new deposits of magnetite were opened. The first pellet plant was built at Eagle Mills in 1954, followed by the first grate/kiln plant at the Humboldt Mine in 1960. The Republic Mine was converted from a shaft mine to an open pit and concentrator in 1956 and a two-kiln pellet plant was added in 1962. The Empire Mine opened in 1963 and was expanded in the mid- and late-1970s; the Pioneer Pellet Plant was opened in 1965 to pelletize the underground ore from the Mather B Mine in Negaunee. In 1974 the Tilden Mine opened in Ishpeming. This mine was and is the only mine in the world with the ability to produce both hematite and magnetite pellets.
Llangolman
The springs emerge in boggy land at the base of the gravel banks, where deposits of blue boulder clay, known by the natives as "indiarubber clay", can also be found. Clay pits close to the farmhouses of Llangolman Farm (still visible) and Llyn are evidence that the clay was once extracted on a significant scale. The study by Jehu mentions that the clay pit at Llyn was down to a depth of 15 to 20 feet, and ladders were required to get in and out. His report goes on to state that the clay is bluish in color and very tough (hence the nickname indiarubber clay). The clay covers the valley bottom from Llyn to Llangolman Farm at a level of over 400 ft.
Clay mineral X-ray diffraction
Well-crystallized and pure samples are ideal for x-ray diffraction, but this is rarely the case for clay. Clay minerals are almost always mixed with very small amounts of nonclay minerals which can produce intense peaks, even when there is very little of the sample is not a clay. If additional minerals are known to be presents, attempts should be made to separate clays from nonclays otherwise additional peaks should be expected. Some common minerals associated with naturally occurring clays are; quartz, feldspars, zeolites, and carbonates organic matter is sometimes present. Synthesis of clays can reduce the presence of some of these associated materials but does not guarantee pure samples as quartz or other associated materials are still commonly produced alongside synthetic clays.
Deep sea mining
Deep sea mining is a relatively new mineral retrieval process that takes place on the ocean floor. Ocean mining sites are usually around large areas of polymetallic nodules or active and extinct hydrothermal vents at below the ocean’s surface. The vents create globular or massive sulfide deposits, which contain valuable metals such as silver, gold, copper, manganese, cobalt, and zinc. The deposits are mined using either hydraulic pumps or bucket systems that take ore to the surface to be processed. As with all mining operations, deep sea mining raises questions about its potential environmental impact. Environmental advocacy groups such as Greenpeace and the Deep sea Mining Campaign have argued that seabed mining should not be permitted in most of the world's oceans because of the potential for damage to deepsea ecosystems and pollution by heavy metal laden plumes.
Pottery
There are several materials that are referred to as clay. The properties which make them different include:
Plasticity, the malleability of the body; the extent to which they will absorb water after firing; and shrinkage, the extent of reduction in size of a body as water is removed. Different clay bodies also differ in the way in which they respond when fired in the kiln. A clay body can be decorated before or after firing. Prior to some shaping processes, clay must be prepared. Each of these different clays are composed of different types and amounts of minerals that determine the characteristics of resulting pottery. There can be regional variations in the properties of raw materials used for the production of pottery, and this can lead to wares that are unique in character to a locality. It is common for clays and other materials to be mixed to produce clay bodies suited to specific purposes. A common component of clay bodies is the mineral kaolinite. Other mineral compounds in the clay may act as fluxes which lower the vitrification temperature of bodies. Following is a list of different types of clay used for pottery.
Clay
Clay minerals typically form over long periods of time as a result of the gradual chemical weathering of rocks, usually silicate-bearing, by low concentrations of carbonic acid and other diluted solvents. These solvents, usually acidic, migrate through the weathering rock after leaching through upper weathered layers. In addition to the weathering process, some clay minerals are formed through hydrothermal activity. There are two types of clay deposits: primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation. Secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Clay deposits are typically associated with very low energy depositional environments such as large lakes and marine basins.
Polymer clay
Polymer clay remains workable until cured generally. Curing occurs at temperatures from between to sustained for 15 minutes per of thickness. This temperature is significantly less than for mineral clays and can be achieved using a home oven. Professional clay brands shrink very little when cured Brands of polymer clay include Fimo, Sculpey, and Kato Polyclay.
Tea pet
A Tea pet is handmade using Zisha (Yixing clay) and unglazed, so it is usually in the natural color of Yixing clay. There are three kinds of Yixing clay: purple clay, red clay, and green clay. A tea pet can be made of either of one of these Yixing clays, or a mixture of two clays to produce different colors.
Parc Slate Quarry
Moses Kellow, who was born on 5 June 1862 at Delabole, Cornwall, close to one of the largest slate quarries in Britain. His parents moved to Caernarfon some three years later, and besides his school education, his father trained him in engineering and geology. By the age of 20, around 1882, he was managing Parc Quarry. Slate in the Blaenau Ffestiniog region is generally found in veins which slope downwards at an acute angle from the horizontal, resulting in the quarries being underground once the initial surface rock has been removed. The veins are separated by layers of harder rock, often granite or chert, which are called "hards". The slate vein worked at Parc Quarry was about thick, and sloped downwards at about 42 degrees. Unusually, the pillaring line, one of the planes in which rock can be split, was almost horizontal rather than vertical, and the foot joints did not run in a suitable direction to detach slate blocks from the floor of a chamber. Additionally, the rock above the vein was not hard enough to support the roof of large chambers. Because of this, Kellow's father, William, decided in 1880 to work the quarry from the bottom upwards, rather than adopting the more normal practice of working from the top downwards.
Mining
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 feasibly 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.
Metal clay
Metal clays are also available as dry powders to which water is added to hydrate and kneaded to attain a clay consistency. One advantage to the powders are their unlimited shelf life. The first silver clay in powder form was released in 2006 as Silver Smiths' Metal Clay Powder. In the following years base metal clays by Hadar Jacobson and Goldie World released several variation containing copper, brass, and even steel.
Cliff mine
The Cliff mine was the first successful copper mine in the Copper Country of the state of Michigan in the United States. The mine is at the now-abandoned town of Clifton in Keweenaw County. Mining began in 1845, and the Cliff was the most productive copper mine in the United States from 1845 through 1854. Large-scale mining stopped in 1878.
Flint mining
Flint mining is the process of extracting flint from underground. Flint mines can be as simple as a pit on the surface or an area of quarrying, or it may refer to a series of shafts and tunnels used to extract flint.
Mining in the United Kingdom
There are many slate mines in the United Kingdom producing slate for building and architectural purposes, of which the largest is the Delabole Slate Mine on the north coast of Cornwall. The United Kingdom also has an abundance of specialized minerals such as china clay, used in fine china and porcelain; and Fuller's earth, an absorbent mineral used for spill containment and cleaning supplies. However, production of Fuller's earth ceased in 2005 in the country.
Mining
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. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. The mines at Grimes Graves and Krzemionki are especially famous, and like most other flint mines, are Neolithic in origin (c. 4000–3000 BC). Other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District.
Slate industry in Wales
In Blaenau Ffestiniog, the Llechwedd Slate Caverns have been converted into a visitor attraction. Visitors can travel on the Miners' Tramway or descend into the Deep Mine, via a funicular railway which uses an old incline, to explore this former slate mine and learn how slate was extracted and processed and about the lives of the miners. The Deep Mine, opened in 1979, is accessed by Britain's steepest passenger railway, with a gradient of 1:1.8 or 30°. In the chambers, formed by slate extraction, sound and light is used to tell the story of the mine and mining. The Braichgoch slate mines at Corris have been converted into a tourist attraction named "King Arthur's Labyrinth" where visitors are taken underground by boat along a subterranean river. They then walk through the caverns to see audiovisual presentations of the Arthurian legends and stories from the Mabinogion and the tales of Taliesin. The Llwyngwern slate quarry near Machynlleth is now the site of the Centre for Alternative Technology. A number of the railways which carried the slates to the ports have been restored as tourist attractions, for example the Ffestiniog Railway and the Talyllyn Railway.
Angar Garia
China clay mines are found in Kharia, Mocdam Nagar, Komarpur, Angargoria and Mohammad Bazar, in Birbhum district. Mining is carried out mainly by the open cast method.
Medicinal clay
The effects of weightlessness on human body were studied by NASA in the 1960s. Experiments demonstrated that weightlessness leads to a rapid bone depletion, so various remedies were sought to counter that. A number of pharmaceutical companies were asked to develop calcium supplements, but apparently none of them were as effective as clay. The special clay that was used in this case was Terramin, a reddish clay found in California. Benjamin Ershoff of the California Polytechnic Institute demonstrated that the consumption of clay counters the effects of weightlessness. He reported that "the calcium in clay ...is absorbed more efficiently ... [clay] contains some factor or factors other than calcium which promotes improved calcium utilization and/or bone formation." He added, "Little or no benefit was noted when calcium alone was added to the diet."
Metal clay
Lump metal clay in bronze was introduced in 2008 by Metal Adventures Inc. and in 2009 by Prometheus. Lump metal clays in copper were introduced in 2009 by Metal Adventures Inc. and Aida. Because of the lower cost, the bronze and copper metal clays are used by artists more often than the gold and silver metal clays in the American market place. The actual creation time of a bronze or copper piece is also far greater than that of its silver counterpart. Base metal clays, such as bronze, copper, and steel metal clays are best fired in the absence of oxygen to eliminate the oxidation of the metal by atmospheric oxygen. A means to accomplish this –- to place the pieces in activated carbon inside a container – was developed by Bill Struve.
Clay
Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger.
Geology of Great Britain
A wide variety of stone has been worked for building and general construction needs (e.g. sand and gravel) while other minerals have been mined or quarried for the chemical industry (e.g. salt), the production of metals (e.g. copper and tin) or other uses (e.g. china clay).
Taoudenni
The Taoudenni mines are located on the bed of an ancient salt lake. The miners use crude axes to dig pits, which usually measure 5 m by 5 m with a depth of 4 m. The miners first remove 1.5 m of red clay overburden, then several layers of poor quality salt before reaching three layers of high quality salt. The salt is cut into irregular slabs that are around 110 cm x 45 cm by 5 cm in thickness and weigh around 30 kg. Two of the high quality layers are of sufficient thickness to be split in half, so that 5 slabs can be produced from the three layers. Having removed the salt from the base area of the pit, the miners excavate horizontally to create galleries from which additional slabs can be obtained.
Slănic mine
Slănic mine is an old salt mine, located in Slănic, Prahova County, Romania, just 100 km north of Bucharest. The salt mine is closed for extraction purposes, but is open for visitors, featuring a microclimate with natural air-conditioning and constant temperature and atmospheric pressure throughout the year. It is made up of two levels, named "Unirea" and "Mihai". Many of the visitors come for its supposed healing effects due to the purity of the air. Throughout the mine you will find various types of equipment for recreational activity such as playground equipment and some ping-pong tables. One area is sectioned off and is being used for medical patients with lung cancer to come and rest. The main elevator shaft is unique in that it has no metallic parts due to rust. After an elevator accident in 2014, minivans are used to spiral visitors up and down.
Thomas Edison
Starting in the late 1870s, Thomas Edison became interested and involved with mining. High-grade iron ore was scarce on the east coast of the United States and Edison tried to mine low-grade ore. Edison developed a process using rollers and crushers that could pulverize rocks up to 10 tons. The dust was then sent between three giant magnets that would pull the iron ore from the dust. Despite the failure of his mining company, the Edison Ore Milling Company, Edison used some of the materials and equipment to produce cement.
Shrink–swell capacity
Due to the physical and chemical properties of some clays (such as the Lias Group) large swelling occurs when water is absorbed. Conversely when the water dries up these clays contract (shrink). The presence of these clay minerals is what allows soils to have the capacity to shrink and swell. Some of these clay minerals are: smectite, nontronite, bentonite, chlorite, montmorillonite, beidellite, attapulgite, illite and vermiculite. The amount of these minerals in a particular soil will also determine the severity of the shrink-swell capacity. For instance, soils with a small amount of expansive clay minerals will not expand as much when exposed to moisture as a soil with a large amount of the same clay minerals. If a soil is composed of at least 5 percent of these clay minerals by weight, it could have the ability to shrink and swell.
Dombes
The clay till which also goes by the now rather old-fashioned but still useful name of boulder clay, is usually very sticky when wet and hard when thoroughly dry. This made arable use of the land with medieval implements impossible and it was unsuitable for pasture most of the time. Usually, such land was left as woodland but here, enterprising landowners seem to have taken it on when nobody else wanted it and attempted to make it produce income by excavating lakes for the raising of fish.
Clay
Studies in the early 21st century have investigated clay's absorption capacities in various applications, such as the removal of heavy metals from waste water and air purification.
Mining in the United Kingdom
The UK is a leading world producer and exporter of china clay and ball clay. Both minerals have a very limited occurrence and it is important that adequate reserves are maintained for long term use. The extraction of china clay results in a significant amount of waste — some 9 tonnes are produced for each tonne of clay.
Yixing ware
Yixing clay () is a type of clay from the region near the city of Yixing in Jiangsu Province, China, used in Chinese pottery since the Song dynasty (960–1279) when Yixing clay was first mined around China's Lake Tai. From the 17th century on, Yixing wares were commonly exported to Europe. The finished stoneware, which is used for teaware and other small items, is usually red or brown in color. Also known as zisha () ware, they are typically left unglazed and use clays that are very cohesive and can form coils, slabs and most commonly slip casts. These clays can also be formed by throwing. The best known wares made from Yixing clay are Yixing clay teapots, tea pets, and other teaware.
Kitchen utensil
There are several types of ceramic utensils.
Terracotta utensils, which are made of red clay and black ceramics. The clay utensils for preparing food can also be used in electric ovens, microwaves and stoves,
we can also place them in fireplaces. It is not advised to put the clay utensil in the 220-250
temperature oven directly, because it will break. It also is not recommended to place the clay pot over an open fire.
Clay utensils do not like sharp change in temperature. The dishes prepared in clay pots come to be
particularly juicy and soft – this is due to the clay’s porous surface. Due to this porous nature of the surface the clay utensils inhale aroma and grease. The coffee made in clay coffee boilers is very aromatic, but such pots need special care. It is not advised to scrub the pots with metal scrubs, it is better to pour soda water in the pot and let it stay there and afterwards to wash the pot with warm water. The clay utensils must be kept in a dry place, so that they will not get damp.
Soil
Before the advent of X-ray diffraction clay was thought to be very small particles of quartz, feldspar, mica, hornblende or augite, but it is now known to be (with the exception of mica-based clays) a precipitate with a mineralogical composition that is dependent on but different from its parent materials and is classed as a secondary mineral. The type of clay that is formed is a function of the parent material and the composition of the minerals in solution. Clay minerals continue to be formed as long as the soil exists. Mica-based clays result from a modification of the primary mica mineral in such a way that it behaves and is classed as a clay. Most clays are crystalline, but some clays or some parts of clay minerals are amorphous. The clays of a soil are a mixture of the various types of clay, but one type predominates.
Dartmoor Preservation Association
The china clay industry on Dartmoor was established long before the DPA was founded. The earliest record of a china clay pit refers to Hook Lake in 1502. The area was surveyed around 1827 by Cornishmen with thirty years experience in the clay industry. They obtained a 21-year lease in 1830, from the Earl of Morley who owned the land, to work the area between Lee Moor and Shaugh Moor. A rival pit was opened at Leftlake in about 1850 and at Hemerdon and Broomage in about 1855. Further pits were opened at Cholwichtown, Whitehill Yeo and Wigford Down/Brisworthy (circa 1860). Others followed at Smallhanger and Headon in the 1870s. Redlake started working in 1910. China clay pits are open cast mines that result in large holes in the ground accompanied by large waste tips. Over time, the pits become larger and more ground is needed for the waste, changing the landscape: the effect of this can be seen from space.
Soil
Due to its high specific surface area and its unbalanced negative electric charges, clay is the most active mineral component of soil. It is a colloidal and most often a crystalline material. In soils, clay is a soil textural class and is defined in a physical sense as any mineral particle less than in effective diameter. Many soil minerals, such as gypsum, carbonates, or quartz, are small enough to be classified as clay based on their physical size, but chemically they do not afford the same utility as do mineralogically-defined clay minerals. Chemically, clay minerals are a range of phyllosilicate minerals with certain reactive properties.
Cloud mining
Cloud Mining is the process of bitcoin mining utilizing a remote datacenter with shared processing power. This type of cloud mining enables users to mine bitcoins or alternative cryptocurrencies without managing the hardware. The mining rigs are housed and maintained in a facility owned by mining company and the customer simply needs to register and purchase mining contracts or shares. Since Cloud Mining is provided as a service there is generally some cost and this can result in lower returns for the miner.
Clay chemistry
The unique properties of clay minerals including: nanometric scale layered construction, presence of fixed and interchangeable charges, possibility of adsorbing and hosting (intercalating) molecules, ability of forming stable colloidal dispersions, possibility of tailored surface and interlayer chemical modification and others, make the study of clay chemistry a very important and extremely varied field of research.
Crushed stone
Stone resources of the world are very large. High-purity limestone and dolomite suitable for specialty uses are limited in many geographic areas. Crushed stone substitutes for roadbuilding include sand and gravel, and slag. Substitutes for crushed stone used as construction aggregates include sand and gravel, iron and steel slag, sintered or expanded clay or shale, and perlite or vermiculite.
Conservation and restoration of ceramic objects
Additionally the type of ceramic will affect how it will break down. Unfired clay, like mud and clay adobe, is clay that is fired under 1000 °C or 1832 °F. This type of clay is water-soluble and unstable. Earthenware is clay that has been fired between 1000-1200 °C or 1832°-2192 °F. The firing makes the clay water insoluble but does not allow the formation of an extensive glassy or vitreous within the body. Although water-insoluble, the porous body of earthenware allows water to penetrate. A glaze can be applied that will protect the vessel from water. Due to its porosity, earthenware is susceptible to moisture and creates problems including cracks, breaks and mold growth. Porcelain and stoneware is fired at the highest temperatures between 1200-1400 °C or 2192-2552 °F. Porcelain clay mixtures are fired to create a non-porous and very hard surface. However, the materials also create a very brittle surface which increases the potential for chips, cracks and breaks.
Expansive clay
Expansive clay is a clay soil that is prone to large volume changes (swelling and shrinking) that are directly related to changes in water content. Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; such soils are called vertisols. Soils with smectite clay minerals, including montmorillonite and bentonite, have the most dramatic shrink-swell capacity.
Yixing ware
The raw materials for yixing clay are buried deep underground, sometimes under heavy sedimentary rock formations. When excavated, it is usually located within stratified layers of other clays. The seam of yixing zisha can be as thick as a several decimeters, up to a meter. Yixing clays consist of fine iron-containing silt, with mica, kaolinite and varying quantities of quartz and iron ores as its main mineral constituents.
Clayton West
There is evidence of 700 years of mining in the adjacent village of Emley. Records from the 13th century indicate that monks from Byland Abby mined and smelted iron ore. They mined using bell pits. A pit was sunk to a depth of 7 meters and worked outward from the bottom of the shaft. Pits dating back to the 16th century can be seen off Woodhouse Lane. Evidence of bell pits is also clearly visible in the woodlands around Duke Wood, down the hill from Cliffe Woods, in Clayton West. Joseph Norton was the owner of a number of mines around the 1870s which he used to mine to produce coal to power his textile mills located at Cuttlehurst and in Scissett. One of these was a mine in Duke Wood. This shaft still acts as an emergency exit and air vent for the privately owned "Flacks" mine, the only mine still operating in the village.
Crisson Mine
In 1969, the owners of Crisson Mine opened to the public to allow tourists to pan for gold. The ore sold for panning is still crushed by the stamp mill, which is now well over 100 years old. It's likely that panning the ore provided at the mine will yield small amounts of gold (flakes, specks, small nuggets).
Geology of Cornwall
The intrusion of the granite into the surrounding sedimentary rocks gave rise to extensive metamorphism and mineralisation, and this led to Cornwall being one of the most important mining areas in Europe until the early 20th century. It is thought that tin ore (cassiterite) was exploited in Cornwall as early as the Bronze Age. Over the years, many other metals such as copper, lead, zinc and silver have all been mined in Cornwall. Alteration of the granite also gave rise to extensive deposits of china clay (kaolinite), especially in the area to the north of St Austell, and this remains one of Cornwall's most important industries.
Dungworth
Load Brook was developed from a farm to a minor industrial site in the late 19th and early 20th centuries. A "pot clay" mine (pot clay – a type of fireclay from the Stannington pot clay bed) was developed to the southwest in the 1850s by William Trickett, a local farmer. Trickett obtained rights to mine pot clay from the landowner, the Duke of Norfolk in 1852 and was mentioned in the Sheffield Trade Directory of 1862 as a clay merchant. William Trickett died in 1890 and the business was continued by his three sons, William, Benjamin and Matthew under the name of B. Trickett & Co.
Brine mining
Salt (sodium chloride) has been a valuable commodity since prehistoric times, and its extraction from sea water also goes back to prehistory. Salt is extracted from seawater in many countries around the world, but the majority of salt put on the market today is mined from solid evaporite deposits.
Rockland Township, Berks County, Pennsylvania
On Beaver Creek was manufactured paper and birch oil. A kind of clay has been found from which chinaware is made. A pottery was also operated in the vicinity. A granite, very much like Vermont granite, is found near New Jerusalem. There is a marble saw mill on the Sacony near Grim's mill, where large blocks of marble are sawed into desirable sizes. It has been in operation since 1864. None of the early mines are now in operation.
Fire clay
Fire clay is resistant to high temperatures, having fusion points higher than ; therefore it is suitable for lining furnaces, as fire brick, and for manufacture of utensils used in the metalworking industries, such as crucibles, saggars, retorts and glassware. Because of its stability during firing in the kiln, it can be used to make complex items of pottery such as pipes and sanitary ware.
Isinuka Mud Caves and Sulphur Pools
Although the clay may be useful for therapeutic and cosmetic purposes, the clay may also constitute a health risk resulting from repeated and unsupervised exposure. There are however, no toxicological studies yet done to identify appropriate beneficial methods to make the clay safer to use.
Open-pit mining
This form of mining differs from extractive methods that require tunneling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface; that is, where the overburden (surface material covering the valuable deposit) is relatively thin or the material of interest is structurally unsuitable for tunnelling (as would be the case for sand, cinder, and gravel). For minerals that occur deep below the surface—where the overburden is thick or the mineral occurs as veins in hard rock—underground mining methods are used to extract the valued material.
Mining
Some mining, including much of the rare earth elements and uranium mining, is done by less-common methods, such as in-situ leaching: this technique involves digging neither at the surface nor underground. The extraction of target minerals by this technique requires that they be soluble, e.g., potash, potassium chloride, sodium chloride, sodium sulfate, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, require acid or carbonate solutions to dissolve.
Marble (toy)
Marbles were originally made by hand. Stone or ivory marbles can be fashioned by grinding. Clay, pottery, ceramic, or porcelain marbles can be made by rolling the material into a ball, and then letting dry, or firing, and then can be left natural, painted, or glazed. Clay marbles, also known as "crock marbles" or "commies" ("common"), are made of slightly porous clay, traditionally from local clay or leftover earthenware ("crockery"), rolled into balls, then glazed and fired at low heat, creating an opaque imperfect sphere that is frequently sold as the poor boy's "old timey" marble. Glass marbles can be fashioned through the production of glass rods which are stacked together to form the desired pattern, cutting the rod into marble-sized pieces using marble scissors, and rounding the still-malleable glass.
Diamond mining in India
As of 2017, there was one industrial-scale diamond mine in India, the Majhgawan mine, near the town of Panna, Madhya Pradesh. The deposit is in a kimberlite or lamproite pipe 6.5 ha in area, and yields 10 carats to the ton. Mining is done by an open pit, which was 85 m deep as of 2011. Exploration drilling has established that the pipe continues down to at least 330 m. The mine is owned by the National Mineral Development Corporation (NMDC), employs 199 people, and has a productive capacity of 84,000 carats per year. The mine began regular production in 1967, and to date, has yielded slightly more than a million carats of diamonds.
Bone Valley
One byproduct of the extraction process is clay, which is stored in settling ponds and eventually comprises 30%-40% of a mine site. Some of these ponds can measure thousands of acres. Rain drains slower through these clay-laden ponds than typical soil. Critics argue that this, in turn, reduces baseflow to the Peace River. Some studies have indicated that reclaimed lands actually provide a more consistent baseflow because the sandier soils of the reclaimed land provide faster baseflow, while the clay provides a slower steady flow, creating more flow during dry periods than native land. Since the 1960s, the average annual flow of the middle Peace River has declined from to per second (38.23 to 22.65 m³/s). Critics argue that this flow reduction is due to phosphate mining, but studies by the Southwest Florida Water Management District have shown that the reduction in flow is due to multidecadal oscillation in Atlantic Ocean temperatures.
Gravel pit
A gravel pit is an open-pit mine for the extraction of gravel. Gravel pits often lie in river valleys where the water table is high, so they may naturally fill with water to form ponds or lakes. Old, abandoned gravel pits are normally used either as nature reserves, or as amenity areas for water sports, landfills and walking. In addition, many gravel pits in the United Kingdom have been stocked with freshwater fish such as the common carp to create coarse fishing locations. Gravel and sand are mined for concrete, construction aggregate and other industrial mineral uses.