معدن 84 آموزش دروس

Talc crystal image by abolfazl abdollahi.

Iron (Fe) is a metallic element and composes about 5% of the Earth’s crust. When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. The reds, oranges and yellows seen in some soils and on rocks are probably iron oxides. The inner core of the Earth is believed to be a solid iron-nickel alloy. Iron-nickel meteorites are believed to represent the earliest material formed at the beginning of the universe. Studies show that there is considerable iron in the stars and terrestrial planets: Mars, the "Red Planet," is red due to the iron oxides in its crust.

Iron is one of the three naturally magnetic elements; the others are cobalt and nickel. Iron is the most magnetic of the three. The mineral magnetite (Fe₃O₄) is a naturally occurring metallic mineral that is occasionally found in sufficient quantities to be an ore of iron.

The principle ores of iron are Hematite, (70% iron) and Magnetite, (72 % iron). Taconite is a low-grade iron ore, containing up to 30% Magnetite and Hematite.

Hematite is iron oxide (Fe₂O₃). The amount of hematite needed in any deposit to make it profitable to mine must be in the tens of millions of tons. Hematite deposits are mostly sedimentary in origin, such as the banded iron formations (BIFs). BIFs consist of alternating layers of chert (a variety of the mineral quartz), hematite and magnetite. They are found throughout the world and are the most important iron ore in the world today. Their formation is not fully understood, though it is known that they formed by the chemical precipitation of iron from shallow seas about 1.8-1.6 billion years ago, during the Proterozoic Eon.

Taconite is a silica-rich iron ore that is considered to be a low-grade deposit. However, the iron-rich components of such deposits can be processed to produce a concentrate that is about 65% iron, which means that some of the most important iron ore deposits around the world were derived from taconite. Taconite is mined in the United States, Canada, and China.

Iron is essential to animal life and necessary for the health of plants. The human body is 0.006% iron, the majority of which is in the blood. Blood cells rich in iron carry oxygen from the lungs to all parts of the body. Lack of iron also lowers a person’s resistance to infection.

The name iron is from an Old English word isaern which itself can be traced back to a Celtic word, isarnon. In time, the "s" was dropped from usage.

It is estimated that worldwide there are 800 billion tons of iron ore resources, containing more than 230 billion tons of iron. It is estimated that the United States has 110 billion tons of iron ore representing 27 billion tons of iron. Among the largest iron ore producing nations are Russia, Brazil, China, Australia, India and the USA. In the United States, great deposits are found in the Lake Superior region. Worldwide, 50 countries produce iron ore, but 96% of this ore is produced by only 15 of those countries.

Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel. Due to the lower cost of foreign-made steel and steel products, the steel industry in the United States has had difficult economic times in recent years as more and more steel is imported. Canada provides about half of the U.S. imports, Brazil about 30%, and lesser amounts from Venezuela and Australia. 99% of steel exported from the USA was sent to Canada.

In the United States, almost all of the iron ore that is mined is used for making steel. The same is true throughout the world. Raw iron by itself is not as strong and hard as needed for construction and other purposes. So, the raw iron is alloyed with a variety of elements (such as tungsten, manganese, nickel, vanadium, chromium) to strengthen and harden it, making useful steel for construction, automobiles, and other forms of transportation such as trucks, trains and train tracks.

While the other uses for iron ore and iron are only a very small amount of the consumption, they provide excellent examples of the ingenuity and the multitude of uses that man can create from our natural resources.

Powdered iron: used in metallurgy products, magnets, high-frequency cores, auto parts, catalyst. Radioactive iron (iron 59): in medicine, tracer element in biochemical and metallurgical research. Iron blue: in paints, printing inks, plastics, cosmetics (eye shadow), artist colors, laundry blue, paper dyeing, fertilizer ingredient, baked enamel finishes for autos and appliances, industrial finishes. Black iron oxide: as pigment, in polishing compounds, metallurgy, medicine, magnetic inks, in ferrites for electronics industry.

Though there is no substitute for iron, iron ores are not the only materials from which iron and steel products are made. Very little scrap iron is recycled, but large quantities of scrap steel are recycled. Steel's overall recycling rate of more than 67% is far higher than that of any other recycled material, capturing more than 1-1/4 times as much tonnage as all other materials combined.

Some steel is produced from the recycling of scrap iron, though the total amount is considered to be insignificant now. If the economy of steel production and consumption changes, it may become more cost-effective to recycle iron than to produce new from raw ore.

Iron and steel face continual competition with lighter materials in the motor vehicle industry; from aluminum, concrete, and wood in construction uses; and from aluminum, glass, paper, and plastics for containers

Tin has been known from ancient times. Ancient peoples found that heating the tin mineral cassiterite (sometimes found in streams as nuggets) in a charcoal fire, they could produce the silvery, soft metal we know as tin.

Tin is a silvery-white metallic element with atomic number 50. Tin is malleable, meaning it is easily shaped by hammering. Pure tin also has a relatively low melting point, easily attainable in a wood fire, and is therefore easy to melt and cast in a clay mold. Tin is stable in air and water, meaning it does not oxidize or react easily . When pure tin is bent rapidly, it makes a peculiar squealing noise: this is called the “tin cry.”

The ancients found tin to be too soft to be of much use for other than decorative objects, and the use of pure tin in ancient times was restricted to mirrors, clasps, and decorative items. Some coins have been minted of tin, but the coins wear and bend rapidly. However, when mixed (alloyed) with copper, another metal which could be found in a nearly pure state in nature, then a new and much harder alloy resulted: bronze. This discovery marked the beginning of the historical period known as The Bronze Age. The advent of the Bronze Age, with the use of bronze spears, arrowheads, knives, sickles, and scythes, greatly enhanced the efficiency of hunters and farmers.

The most important ore mineral of tin, cassiterite (tin dioxide, SnO2) forms in high-temperature veins, usually related to igneous rocks such as granites and rhyolites. It is often found in association with tungsten minerals. When rocks containing cassiterite are weathered (decomposed by the action of surficial waters and oxidation), the cassiterite tends to remain intact, and eventually is concentrated in streams to form “placer” deposits, in a manner similar to gold nuggets in “placer” deposits. Ancient peoples recovered cassiterite from streams by panning, and even today panning or - more importantly - large-scale mechanical dredging of stream deposits and decomposed rock are a major means of producing cassiterite. Veins with a high enough cassiterite content to mine underground occur in China, Bolivia, Peru, and a few other countries.

The name tin is an ancient Anglo-Saxon word. Tin in the form of cassiterite was mined in ancient Britain and was a major trade item between Britain and the Greeks and Phoenicians of the Mediterranean region. The chemical symbol for tin, Sn, comes from the Latin word for tin, stannum. Tin was one of only seven chemical elements known in pure form, and named by ancient peoples. The mineral cassiterite is named for the ancient Greek word for tin.

As noted earlier, the primary mineral source for tin is cassiterite. The most tin resources in the United States are in Alaska, but these are relatively insignificant, and the U.S. has long imported its tin from other countries.

World resources to meet the demand for tin are sufficient for many decades to come. The primary producers of tin are China, Indonesia, and Peru, with lesser amounts from Brazil, Bolivia, Australia, and about a dozen other countries.

Much tin is used to coat so-called “tin” cans. Since tin does not oxidize (rust) in air or water, it is applied to the surface of flat-rolled steel to make tin plate, which is then fabricated to produce “tin” cans. This use accounts for about one-fourth of the tin consumed annually. Alloys such as bronze and pewter are also a major use of tin. Tin is useful in electrical applications, mainly low-melting-point solders, that account for one-fourth of tin consumption. It is also used in construction, transportation (mainly in bearings requiring soft metal alloys) and other various industrial applications. For example, window glass is made by pouring molten glass onto molten tin; this process results in flat sheets of glass. An alloy of tin and niobium has proven to be a “superconducting” compound at very low temperatures.

Mica is a mineral name given to a group of minerals that are similar in their physical properties and chemical compositions. They are all silicate minerals, which means that chemically they all contain silica(SiO₄). Mineralogists call micas sheet silicates because their molecules combine to form distinct layers. These layers can be seen in muscovite mica specimens because it can be split (mineralogists call this feature cleavage) into very thin, flexible, transparent layers. This physical property is so distinctive that all minerals that cleave in this fashion are said to have micaceous cleavage.

There are 37 different mica minerals. In addition to the silicate tetrahedrons in all micas, Purplemicaceous cleavage.

Scrap and flake mica is produced all over the world. In the U.S., scrap and flake mica was produced in Arizona, North Carolina, South Dakota, Georgia, New Mexico and South Carolina. North Carolina's production accounts for half of total U.S. mica production. The flake mica produced in the U.S. comes from several sources: the metamorphic rock called schist as a by-product of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Canada, India, Finland, and Japan export flake mica to the U.S.

Sheet mica is considerably less abundant than flake and scrap mica. Sheet mica is occasionally recovered from mining scrap and flake mica. The most important sources of sheet mica are the pegmatite deposits. The United States has limited sheet mica resources. U.S. mining of sheet mica is costly and labor costs are high. As a result, the U.S. imports more than half its sheet mica from India, but also from Belgium, Germany, China, and a few other countries.

The principal use of ground mica is in gypsum wallboard joint compound, where it acts as a filler and extender, provides a smoother consistency, improves workability, and prevents cracking. In the paint industry, ground mica is used as a pigment extender that also facilitates suspension due to its light weight and platy morphology. The ground mica also reduces checking and chalking, prevents shrinkage and shearing of the paint film, provides increased resistance to water penetration and weathering, and brightens the tone of colored pigments. Ground mica also is used in the well-drilling industry as an additive to drilling “muds.”

Coarsely ground mica flakes help prevent lost circulation by sealing porous sections of the uncased drill hole. The plastic industry used ground mica as an extender and filler and also as a reinforcing agent. The rubber industry uses ground mica as an inert filler and as a mold lubricant in the manufacture of molded rubber products, including tires.

Sheet mica is used principally in the electronic and electrical industries. The major uses of sheet and block mica are as electrical insulators in electronic equipment, thermal insulation, gauge “glass”, windows in stove and kerosene heaters, dielectrics in capacitors, decorative panels in lamps and windows, insulation in electric motors and generator armatures, field coil insulation, and magnet and commutator core insulation. Mica is also used as segment plates between copper commutator sections to insulate copper from the steel; phlogopite mica is used because it wears at the same rate as the copper segments.

Some lightweight mineral and rock materials, such as vermiculite, diatomite and perlite are similar to micas and can be used in place of mica. A long list of manufactured materials, such as styrene, polyester, Teflonâ , Plexiglassâ , etc., can be used in place of sheet mica in the electronic applications. Paper made from ground mica can be used in place of sheet mica for insulating applications.

Cobalt is a bluish-gray, shiny, brittle metallic element. Its atomic number is 27 and its symbol is Co. It belongs to a group of elements called the transition metals. It has magnetic properties like iron.

Ancient civilizations in Egypt and Mesopotamia used a substance to color glass a beautiful deep blue. In 1735, the Swedish scientist Georg Brandt set out to prove that this color was due not to the element bismuth, as people believed, but to a new and unidentified element. He is credited with the discovery of this new element, which he named cobalt.

Cobalt is one of the elements that is very important to life, including human life and health. Vitamin B-12 contains cobalt. In areas where there is little cobalt in the soil, farmers have to provide salt blocks containing cobalt for their animals to lick in order to provide enough cobalt in their diet.

Cobalt is also found in iron-nickel meteorites.

Cobalt was named after the German word kobald which means goblin or evil spirit believed to cause health problems for silver and copper miners.

It is estimated that there are about 1 million tons of cobalt in the United States. Minnesota has the largest resources, but other ore resources are found in Alaska, California, Idaho, Missouri, Montana and Oregon. The identified cobalt resources in the world total about 15 million tons. Most are found in Australia, Canada, Congo, Russia, and Zambia.

The ocean floor has nodules of metals that form when hot water from deep in the Earth comes into contact with the cold ocean water. These nodules are mostly manganese and so are called manganese nodules. It is estimated that there are millions of tons of cobalt in these nodules. Presently, we do not have the technology to retrieve these nodules at a reasonable cost.

All of the primary cobalt used in the U.S. is imported. Cobalt is imported into the United States in the form of cobalt metal, cobalt salts, and cobalt oxide. The imports come from Norway, Finland, Canada, Russia, and other nations.

Cobalt has been used by civilizations for centuries to create beautiful deep blue glass, ceramics, pottery and tiles. In a similar way, it is being used to make paint pigments.

In addition to these traditional uses, cobalt is used in a number of industrial applications. When cobalt is alloyed with other metals, very strong magnets are created. Superalloys containing cobalt are used in the production of jet engines and gas turbine engines for energy generation. These superalloys account for nearly half of the cobalt used each year. Some cobalt is used to make cutting and wear-resistant materials.

A manmade isotope of cobalt, cobalt-60, produces gamma rays. This is used for sterilization of medical supplies and foods, for industrial testing, and to fight cancer.

Because of the toxic nature of beryllium, careful control over the quantity of dust and fumes in the workplace must be maintained.

Beryllium was not known to ancient or medieval civilizations, and was first recognized by the French scientist, Nicholas Louis Vauquelin in 1798. He discovered it as a component of the mineral beryl, and named it beryllium. Metallic beryllium was not isolated until 1828, by Friederich Wˆhler in Germany.

The most common mineral containing beryllium is beryl, a silicate mineral with the chemical formula Be₃Al₂Si₆O₁₈.  Beryl forms distinctive hexagonal prisms, and is found in the igneous rock granite and special igneous rocks, derived from granites, known as pegmatites. Colored, transparent varieties of beryl may be gems, such as emerald (green), aquamarine (blue-green), heliodor (yellow), and morganite (pink). In addition to being found in beryl, beryllium is found in the mineral bertrandite Be4Si2O7(OH)2, which in recent years has become a major ore of this element, in addition to beryl. Bertrandite is found in certain volcanic rocks derived from granite. 

Bertrandite ore mined in Utah makes up nearly all of U.S. production, which is about two-thirds of the world supply. Russia produces most of the rest, from beryl ores. Five to ten other countries mine small amounts of beryl. The United States produces and exports large amounts of beryllium alloys and compounds, and thus is a net importer of ores, but a net exporter of finished beryllium products.

Small amounts of beryllium become available from recycling of beryllium-containing scrap.

Most beryllium is used in metal alloys, which account for more than 70% of world consumption. Because beryllium is very light and has a high melting temperature, it is an ideal metal for use in the aerospace and defense industry, almost always alloyed with other metals. Beryllium metal also has the interesting characteristic of being elastic. Consequently, it is used in the manufacture of springs, gears and other machine components that need a degree of elasticity. Another everyday application is in the manufacture of gasoline pumps, because an alloy of copper and beryllium (beryllium bronze) does not spark when hit against other metals, nor emit sparks from static electricity.

Rods made of beryllium metal and oxide are used to control nuclear reactions, because beryllium absorbs neutrons better than any other metal.

Most organisms do not depend on beryllium for growth. In fact, beryllium dust and fumes can be dangerous to human health when inhaled. Consequently, the Clean Air Act demands very careful handling of beryllium dust and fumes to minimize or eliminate its danger to humans.