Text 14. STALACTITE AND STALAGMITE
Stalactite and Stalagmite are mineral formations frequently found in caves. A stalactite is an icicle-shaped mass of accumulated calcium carbonate hanging from the roof or sides of a limestone cavern; it is formed by mineral precipitation from groundwater that has seeped, very slowly, through the roof of the cavern. Water circulating through the ground above a cavern picks up calcium bicarbonate as it percolates through the limestone. When the water trickles through the ground to the roof of a cavern, it tends to cling to the roof in droplets; as the droplets lose some of their water and carbon dioxide, calcium carbonate is precipitated and forms a deposit. As more water seeps through the roof, the precipitation of calcium carbonate continues and the deposits grow in length and width, forming stalactites; these are often of enormous size and beautiful shape.
Pure calcium carbonate is white, but stalactites are often variously colored by impurities in the mineral. Some of the water seepage also falls to the floor and there accumulates into calcium carbonate masses resembling inverted stalactites. These deposits, growing upward from the floor, are called stalagmites. Stalactites and stalagmites often occur in pairs and meet, forming columns that may grow as large as 1.5 m (5 ft) in diameter.
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Text 15. SALT
Salt,also sodium chloride, is a chemical compound that has the formula NaCl. The term salt is also applied to substances produced by the reaction of an acid with a base, known as a neutralization reaction. Salts are characterized by ionic bonds, relatively high melting points, electrical conductivity when melted or when in solution, and a crystalline structure when in the solid state.
Salt is a white solid, soluble in hot or cold water, slightly soluble in alcohol, but insoluble in concentrated hydrochloric acid. In the crystalline form the compound is transparent and colorless, shining with an icelike luster. The compound usually includes traces of magnesium chloride (MgCl2), magnesium sulfate (MgSO 4), calcium sulfate (CaSO4), potassium chloride (KCl), and magnesium bromide (MgBr2).
Salt is widely distributed in nature. It is found in solution in ocean water in concentrations of about 30 g/liter of water, meaning that salt makes up about 3 percent of ocean water by weight. Salt can occur as a surface crust or layer in swamps and dry lake bottoms, especially in extremely arid regions. The mineral halite, more commonly known as rock salt or massive salt, occurs in beds deposited by the dehydration of ancient bodies of salt water. The compound is constantly being formed by the action of rivers and streams on rocks containing chlorides and compounds of sodium. Salt melts at 804° C (1479° F) and begins to vaporize at temperatures just slightly above this; it has a specific gravity of 2.17.
Uses. The most familiar use of salt is as a seasoning. Salt is an essential constituent in the diet of human beings and other warm-blooded animals. Certain peoples restrict the consumption of salt, but they obtain necessary quantities of it by eating salt-containing raw or cooked meat and fish. Wild animals often congregate at salt streams or surface encrustations of salt, called salt licks, where they lick the salt deposits.
Industrially, salt is the source of chlorine and its principal compounds and the source of sodium and its compounds. Chlorine compounds of commercial importance include hydrochloric acid, chloroform, carbon tetrachloride, and bleaching powder. Important sodium compounds include sodium carbonate, sodium sulfate, baking soda, sodium phosphate, and sodium hydroxide. Salt is widely used as a preservative for meats and is employed in some refrigeration processes, in dyeing, and in the manufacture of soap and glass. Because they are transparent to infrared radiation, salt crystals are used for making the prisms and lenses of instruments used in the study of infrared radiation.
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Text 16. HALITE
Halite is a mineral form of common salt, with the chemical composition sodium chloride, NaCl. Halite, also called rock salt, is a common mineral, formed by the drying of enclosed bodies of salt water; subsequently the beds so formed have often been buried by the rock strata formed from other sedimentary deposits. Beds of halite range in thickness from a few meters to 30 m and have been found at great depths beneath the surface of the earth. This mineral is often found associated with gypsum, sylvite, anhydrite, calcite, clay, and sand. Halite is widely disseminated over the world.
Halite crystallizes in the isometric system, usually in the form of cubes, and shows perfect cubic cleavage. It is colorless and transparent when pure but is often tinted yellow, red, blue, or purple by impurities. It has a hardness of 2.5 and a specific gravity of 2.16.
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Text 17. GYPSUM
Gypsumis a common mineral consisting of hydrated calcium sulfate (CaSO4·2H2O). It is a widely distributed form of sedimentary rock, formed by the precipitation of calcium sulfate from seawater, and is frequently associated with other saline deposits, such as halite and anhydrite, as well as with limestone and shale. Gypsum is produced in volcanic regions by the action of sulfuric acid on calcium-containing minerals; it is also found in most clays as a product of the action of sulfuric acid on limestone. It occurs in all parts of the world; some of the best workable deposits are in France, Switzerland, and Mexico. Alabaster, selenite, and satin spar are varieties of gypsum.
Artificial gypsum is obtained as a by-product in an old method for the manufacture of phosphoric acid. Phosphate rock, the essential constituent of which is tricalcium phosphate, is treated with sulfuric acid, producing phosphoric acid and gypsum. The gypsum is compacted into blocks and used for the construction of nonsupporting walls in buildings. By properly controlling the concentration and temperature of sulfuric acid added to phosphate rock, a mixture of monocalcium phosphate, dicalcium phosphate, and gypsum may be obtained. This mixture is a valuable fertilizer, superphosphate.
Gypsum crystallizes in the monoclinic system in white or colorless crystals, massive or foliated in formation. Many specimens are colored green, yellow, or black by impurities. With a hardness ranging from 1.5 to 2, it is soft enough to scratch with a fingernail and has a specific gravity of 2.3.
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NOTES:
· saline – солончак, соленый источник;
· spar - шпат.
Text 18. SELENITE
Selenite (Greek selзnз, "moon") is a variety of gypsum that occurs in transparent crystals or crystalline masses. It is so called because, according to a legend of Central Europe, the crystals form when the moon is on the increase. Extremely large crystals of selenite are found in southern Utah in geodes, or hollow rocks. Broad, transparent sheets of selenite can be split into extremely thin, transparent plates, which were used by the ancients in place of glass. Selenite today is quarried and used as ordinary gypsum.
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Text 19. ALABASTER
Alabaster is a varietal name applied to two different minerals. One, Oriental alabaster, was extensively used by the ancient Egyptians. It is a variety of calcite, with a hardness of 3; it is usually white and translucent, but is often banded with dark or colored streaks. The other mineral, true alabaster, is a variety of gypsum, usually snow-white in color with a uniform, fine grain. True alabaster is softer than Oriental alabaster; it has a hardness of 1.5 and is easily carved into intricate shapes. Deposits of fine gypsum alabaster are found in Italy, England, Iran, and Pakistan.
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Text 20. BASALT
Basalt is the most common variety of volcanic rock, composed almost entirely of dark, fine-grained silicate minerals, chiefly plagioclase feldspar and pyroxene, and magnetite. The extrusive equivalent of gabbro, it forms by the outpouring of lava all along the world’s mid-ocean ridges, where sea-floor spreading continually adds new crust to counterbalance that lost by subduction. Usually dark-gray in color, basalt often has a vesicular texture, preserving vestiges of bubbles produced by expanding steam as lava cools and solidifies. Also characteristic are pillow-shaped masses caused by rapid cooling of lava erupted on the sea floor. In addition to lava flows, basalt is also found in the form of dikes and sills. Columnar jointing, as exhibited by Devils Tower in Wyoming and the Giant’s Causeway in Ireland, is a common feature of these shallow intrusive bodies.
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NOTES:
· gabbro – габбро.
Text 21. GOLD
Gold, symbol Au (from Latin aurum,"gold"), is a soft, dense, bright yellow metallic element. Gold is one of the transition elements of the periodic table; its atomic number is 79.
Properties. Pure gold is the most malleable and ductile of all the metals. It can easily be beaten or hammered to a thickness of 0.000013 cm, and 29 g could be drawn into a wire 100 km long. It is one of the softest metals (hardness, 2.5 to 3) and is a good conductor of heat and electricity. Gold is bright yellow and has a high luster. Finely divided gold, like other metallic powders, is black; colloidally suspended gold ranges in color from ruby red to purple.
Gold is extremely inactive. It is unaffected by air, heat, moisture, and most solvents. It will, however, dissolve in aqueous mixtures containing various halogens such as chlorides, bromides, or some iodides. It will also dissolve in some oxidizing mixtures, such as cyanide ion with oxygen, and in aqua regia, a mixture of hydrochloric and nitric acids. The chlorides and cyanides are important compounds of gold. Gold melts at about 1064° C (about 1947° F), boils at about 2808° C (about 5086° F), and has a specific gravity of 19.3; its atomic weight is 196.97.
Occurrence. Gold is found in nature in quartz veins and secondary alluvial deposits as a free metal or in a combined state. It is widely distributed although it is rare, being 75th in order of abundance of the elements in the crust of the earth. It is almost always associated with varying amounts of silver; the naturally occurring gold-silver alloy is called electrum. Gold occurs, in chemical combination with tellurium, in the minerals calaverite and sylvanite along with silver, and in the mineral nagyagite along with lead, antimony, and sulfur. It occurs with mercury as gold amalgam. It is generally present to a small extent in iron pyrites; galena, the lead sulfide ore that usually contains silver, sometimes also contains appreciable amounts of gold. Gold also occurs in seawater to the extent of 5 to 250 parts by weight to 100 million parts of water. Although the quantity of gold present in seawater is more than 9 billion metric tons, the cost of recovering the gold would be far greater than the value of the gold that could thus be recovered.
Uses. The metal has been known and highly valued from earliest times, not only because of its beauty and resistance to corrosion, but also because gold is easier to work than all other metals. In addition, gold was easier to obtain in pure form than the other metals. Because of its relative rarity, gold became used as currency and as a basis for international monetary transactions. The unit used in weighing gold is the troy ounce; 1 troy ounce is equivalent to 31.1 grams.
The major portion of the gold produced is used in coinage and jewelry. For these purposes it is alloyed with other metals to give it the necessary hardness. The gold content in alloys is expressed in carats. Coinage gold is composed of 90 parts gold to 10 parts silver. Green gold used in jewelry contains copper and silver; white gold contains zinc and nickel, or platinum metals.
Gold is also used in the form of gold leaf in the arts of gilding and lettering. Purple of Cassius, a precipitate of finely divided gold and stannic hydroxide formed by the interaction of auric chloride and stannous chloride, is used in coloring ruby glass. Chlorauric acid is used in photography for toning silver images. Potassium gold cyanide is used in electrogilding. Gold is also used in dentistry. Radioisotopes of gold are used in biological research and in the treatment of cancer.
South Africa is the world’s leading supplier of gold, producing about 600 metric tons annually; its most important gold mines are in the Witwatersrand region. Some 70 other countries produce gold in commercial quantities, but about 80 percent of the total worldwide production now comes from South Africa, the United States, the former Soviet republics, Australia, Canada, China, and Brazil.
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NOTES:
· malleable - ковкий (о металле);
· alluvial - рассыпной (о золоте);
· antimony - сурьма;
· troy ounce - тройская унция (31,1035 г);
· gilding - позолота, золочение.
Text 22. PETROLEUM
Petroleum, or crude oil, is naturally occurring oily, bituminous liquid composed of various organic chemicals. It is found in large quantities below the surface of the earth and is used as a fuel and as a raw material in the chemical industry. Modern industrial societies use it primarily to achieve a degree of mobility - on land, at sea, and in the air - that was barely imaginable less than a hundred years ago. In addition, petroleum and its derivatives are used in the manufacture of medicines and fertilizers, foodstuffs, plastic ware, building materials, paints, and cloth and to generate electricity.
In fact, modern industrial civilization depends on petroleum and its products; the physical structure and way of life of the suburban communities that surround the great cities are the result of an ample and inexpensive supply of petroleum. In addition, the goals of developing countries - to exploit their natural resources and to supply foodstuffs for the burgeoning populations - are based on the assumption of petroleum availability. In recent years, however, the worldwide availability of petroleum has steadily declined and its relative cost has increased. Petroleum will probably no longer be a common commercial material by the mid-21st century.
Characteristics. The chemical composition of all petroleum is principally hydrocarbons, although a few sulfur-containing and oxygen-containing compounds are usually present; the sulfur content varies from about 0.1 to 5 percent. Petroleum contains gaseous, liquid, and solid elements. The consistency of petroleum varies from liquid as thin as gasoline to liquid so thick that it will barely pour. Small quantities of gaseous compounds are usually dissolved in the liquid; when larger quantities of these compounds are present, the petroleum deposit is associated with a deposit of natural gas.
Three broad classes of crude petroleum exist: the paraffin types, the asphaltic types, and the mixed-base types. The paraffin types are composed of molecules in which the number of hydrogen atoms is always two more than twice the number of carbon atoms. The characteristic molecules in the asphaltic types are naphthenes, composed of twice as many hydrogen atoms as carbon atoms. In the mixed-base group are both paraffin hydrocarbons and naphthenes.
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NOTES:
· bituminous – битумный, битуминозный;
· crude petroleum – сырая нефть.
Text 23. A.Y. FERSMAN
A.Y. Fersman (1883-1945) was the great Russian mineralogist and geochemist, one of the founders of the Russian geochemical school.
Academician A.Y. Fersman ranks among those leading scientists (M.V. Lomonosov, A.P. Karpinsky, V.A. Obruchev, I.M. Gubkin, V.I. Vernadsky) who converted mineralogy from a purely descriptive science into a science based on the most fundamental chemical investigations. As the organizer of the Geochemical Institute in Moscow, Academician Fersman worked out the basic lines of the study of chemical elements and laid the foundation for the scientific surveying and prospecting for useful minerals.
A number of scientific expeditions to different parts of the country were organized by him. Fersman was the leader of the important investigations in the Kara-Kum Desert resulting in the discovery of big sulphur deposits, the construction of a large preparation plant for the processing of sulphur and sulphur products. He led the expedition to Central Asia, the Urals, the Altai, the Caucasus and the Crimea.
Academician Fersman is especially known for his detailed investigations of the Kola Peninsula which led to the discovery of enormous apatite deposits and the development of a mining-industrial region in the Khibiny Mountains where new towns came into being.
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PART III
Text 1. PJSC “APATIT”
Public joint stock company (PJSC) "Apatit" is the largest producer of phosphoric raw materials in Europe. The company was founded in 1929 on the base of unique reserves of apatite-nepheline ore deposit of Khibiny group. The apatite-nepheline ores are unique in terms of their mineral composition. On their base it is possible to produce five concentrates which can be used in many industrial sectors. PJSC "Apatit" is a city-building enterprise and on this bases the city Kirovsk and Apatity with 120 thousand population were constructed. Substantial housing resources, culture palaces, hotels, recreation centres, sport complexes and other units create the large social infrastructure.
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