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Physical and chemical properties of gold, sample of gold. Chemical formula of gold

Gold(lat. aurum), au, chemical element of group 1 of Mendeleev's periodic system; atomic number 79, atomic mass 196.9665; heavy yellow metal. Consists of one stable isotope 197 au.

Historical reference. Z. was the first metal known to man. Articles made of gold have been found in the cultural layers of the Neolithic period (5th-4th millennia BC). In the ancient states — Egypt, Mesopotamia, India, and China — mining of gold and the making of jewelry and other items from it existed for 3–2 thousand BC. NS. Z. is often mentioned in the Bible, the Iliad, the Odyssey, and other monuments of ancient literature. Alchemists called Z. "the king of metals" and designated him as the symbol of the sun; the discovery of methods for converting base metals into gold was the main goal alchemy.

Prevalence in nature. The average gold content in the lithosphere is 4.3 · 10 -7% by weight. Gold is dispersed in magma and igneous rocks, but hydrothermal deposits of gold are formed from hot waters in the earth's crust, which are of great industrial importance (quartz gold-bearing veins, etc.). In ores gold is mainly found in a free (native) state and only very rarely forms minerals with selenium, tellurium, antimony, and bismuth. Pyrite and other sulfides often contain an admixture of gold, which is extracted during the processing of copper, polymetallic, and other ores.

In the biosphere, gold migrates in combination with organic compounds and mechanically in river suspensions. 1 l sea ​​and river water contains about 4 · 10 -9 G H. In areas of gold ore deposits, groundwater contains gold approximately 10 -6 g / l. It migrates in soils and from there enters the plants; some of them concentrate gold, for example, horsetails and corn. The destruction of endogenous gold deposits leads to the formation of industrial gold placers. Gold is mined in 41 countries; its main reserves are concentrated in the USSR, South Africa and Canada.

Physical and chemical properties. Z. - soft, very ductile, ductile metal (can be forged into sheets up to 8 10 -5 mm, stretched into the wire, 2 km which weigh 1 G), conducts heat and electricity well, very resistant to chemical influences. The crystal lattice of the gold is face-centered cubic. a = 4.704 a. Atomic radius 1.44 a, ionic radius au 1+ 1.37 a. Density (at 20 ° C) 19.32 g / cm 3, t pl 1064.43 ° C, t kip 2947 ° C; thermal coefficient of linear expansion 14.2 · 10 -6 (0-100 ° C); specific thermal conductivity 311.48 tue/(m· TO) ; specific heat 132.3 j/(Kg K) (at 0 ° -100 ° C); specific electrical resistance 2.25 · 10 -8 ohm(m(2.25 10 -6 ohm(cm) (at 20 ° C); temperature coefficient of electrical resistance 0.00396 (0-100 ° С). Elastic modulus 79 103 Mn / m 2(79 10 2 kgf / mm 2), for annealed gold. tensile strength 100-140 Mn / m 2(10-14 kgf / mm 2), elongation 30-50%, cross-sectional narrowing 90%. After plastic deformation in the cold, the tensile strength increases to 270-340 Mn / m 2 (27-34 kgf / mm 2) . Brinell hardness 180 Mn / m 2 (18 kgf / mm 2) (for gold annealed at about 400 ° C).

The configuration of the outer electrons of the atom Z. 5d 10 6s 1. In compounds, gold has valences of 1 and 3 (complex compounds are known in which gold is 2-valent). Gold does not interact with non-metals (except for halogens). With halogens gold forms halides, for example 2au + 3cl 2 = 2auc13. Gold dissolves in a mixture of hydrochloric and nitric acids, forming chloroauric acid h. In solutions of sodium cyanide nacn (or potassium kcn), with the simultaneous access of oxygen, gold is converted into sodium cyanoaurate (i) 2na. This reaction, discovered in 1843 by P.R. Bagration, received practical application only at the end of the 19th century. Gold is characterized by its easy reducibility from compounds to metal and the ability to form complexes. The existence of gold oxide, that is, gold oxide (i) au 2 o, is doubtful. Z. chloride (i) aucl is obtained by heating Z. chloride (iii): auc1 3 = aucl + c1 2.

Chloride Z. (iii) auc1 3 is obtained by the action of chlorine on powder or thin leaves of Z. at 200 ° C. Red needles auc1 3 give a brown-red solution of complex acid with water: auc1 3 + Н 2 О = Н 2.

When the solution of auc1 3 is precipitated with a caustic alkali, the amphoteric yellow-brown hydroxide Z is precipitated. (Iii) au (oh) 3 with a predominance of acidic properties; therefore it is called golden acid, and its salts are called aurat (iii). When heated, gold hydroxide (iii) is converted into gold oxide au 2 o 3, which decomposes above 220 ° by the reaction:

2au 2 o 3 = 4au + 3o 2.

In the reduction of gold salts with tin (ii) chloride 2auc1 3 + 3sncl 2 = 3sncl 4 + 2au

a very stable purple colloidal solution of gold is formed (cassian purple); this is used in analysis for the detection of gold. The quantitative determination of gold is based on its precipitation from aqueous solutions by reducing agents (feso 4, h 2 so 3, h 2 c 2 o 4, etc.) or on the use of assay analysis.

Getting Z. and its refining. Gold can be extracted from placer deposits by elutriation, based on the large difference in the densities of gold and waste rock. This method, which was already used in ancient times, is associated with great losses. He gave way amalgamation(known already in the 1st century BC and used in America since the 16th century) and cyanidation, which became widespread in America, Africa and Australia in the 1890s. In the late 19th - early 20th centuries. Primary deposits became the main source of gold. Gold-bearing rock is first subjected to crushing and beneficiation. Gold is extracted from the resulting concentrate with a solution of potassium or sodium cyanide. Zinc is precipitated from the complex cyanide solution; in this case, impurities also fall out. For purification (refining) of gold by electrolysis (E. Wolville's method, 1896), anodes cast from unclean gold are suspended in a bath containing a hydrochloric acid solution of auc1 3; a sheet of pure gold serves as the cathode. , sludge), and gold is deposited on the cathode with a purity of at least 99.99%.

Application ... Z. in the conditions of commodity production performs the function of money... In technology, gold is used in the form of alloys with other metals, which increases the strength and hardness of gold and makes it possible to save it. The gold content in alloys used for the manufacture of jewelry, coins, medals, semi-finished products of denture production, etc., is expressed as breakdown; usually the additive is copper (the so-called ligature). Alloyed with platinum, gold is used in the manufacture of chemically resistant equipment, and alloys with platinum and silver in electrical engineering. Gold compounds are used in photography (toning).

S. A. Pogodin.

Z. in art. Z. has been used since ancient times in jewelry art(decorations, cult and palace utensils, etc.), as well as for gilding. Due to its softness, malleability, and the ability to stretch, gold lends itself to particularly fine processing by chasing, casting, and engraving. Z. is used to create a variety of decorative effects (from the smooth surface of a yellow polished surface with smooth tints of light reflections to complex textured juxtapositions with a rich light and shadow play), as well as to perform the finest filigree. Z., often colored with impurities of other metals in various colors, is used in combination with precious and ornamental stones, pearls enamel, niello.

In medicine, medicinal products are used in the form of a suspension in oil (the domestic drug Krizanil, the foreign one, myocrizin) or water-soluble drugs (foreign ones, Sankrizin and Solganal) for injection in the treatment of chronic rheumatic arthritis, erythematous lupus erythematosus, often in combination with hormonal drugs, etc. drugs. Z. preparations often cause side effects (an increase in body temperature, irritation of the intestines, kidneys, etc.). Contraindications to the use of medicinal products: severe forms of tuberculosis, diabetes mellitus, diseases of the cardiovascular system, liver, kidneys, and blood.

Radioactive gold (usually 198 au) is injected into tissues in the form of pins, granules, and the like. - for gamma therapy and in the form of colloidal solutions - for beta therapy. It is used in the treatment of tumors, usually in combination with surgical and drug treatment, as well as for diagnostic purposes - in the form of colloidal solutions in the study of the reticuloendothelial system, liver, spleen, and other organs.

Lit .: Plaksin IN, Gold, in the book: Brief chemical encyclopedia, t. 2, M., 1966; Remy G., Course in inorganic chemistry, trans. from it., t. 2, M., 1966, p. 439-451; ullmanns enzykiop a die dertechnischen chemie, 3 aufl., bd 8, m u nch. - b., 1957, s. 253-307; Magakyan I.G., Ore Deposits, 2nd ed., Er., 1961; Russian gold and silver business of the 15-20 centuries, M., 1967 (bibl. Pp. 289-93); rosenberg M., geschichte der goldschmiedekunst auf technischer grundlage, fr./m., 1918.

Economic significance. Under conditions of commodity production, gold performs the function of a universal equivalent. "The first function of gold is to provide the commodity world with material for expressing value, that is, in order to express the value of goods as quantities of the same name, qualitatively identical and quantitatively comparable" (K. Marx, in the book: K. and F. Engels, Soch., 2nd ed., vol. 23, p. 104). Expressing the value of all other commodities, gold as a universal equivalent acquires a special use value, becomes money. "Gold and silver by their nature are not money, but money by their nature - gold and silver" (K. Marx, ibid., Vol. 13, p. 137). The world of commodities singled out gold as money because it possesses the best physical and chemical properties for a money commodity: homogeneity, divisibility, preservation, portability (high value for a small volume and weight), and can be easily processed. A significant amount of gold is used for the manufacture of coins or in the form of ingots is stored as a gold reserve of central banks (states). Gold is widely used for industrial consumption (in radio electronics, instrument making, and other progressive industries), and also as a material for making jewelry.

Initially, gold was used exclusively for making ornaments; later, it began to serve as a means of saving and accumulating wealth, as well as exchange (first in the form of ingots). Z. was used as money as early as 1500 BC. NS. in China, India, Egypt and the states of Mesopotamia, and in Ancient Greece - in the 8-7 centuries. BC NS. In Lydia, rich in gold deposits, in the 7th century. BC NS. the minting of the first coins in history began. The name of the Lydian king Croesus (reigned about 560-546 BC) has become synonymous with untold wealth. On the territory of the USSR (in Armenia) coins from Z. were minted in the 1st century. BC NS. But in antiquity and in the Middle Ages, gold was not the main currency metal. Along with it, the functions of money were performed by copper and silver.

The pursuit of Z. and a passion for enrichment were the reasons for numerous colonial and trade wars, and during the era of the great geographical discoveries they were pushed to search for new lands. The flow of precious metals to Europe after the discovery of America was one of the sources initial capital accumulation. Until the middle of the 16th century. From the New World, gold was imported to Europe mainly (97-100% of the imported metal), and from the second third of the 16th century, after the discovery of the richest silver deposits in Mexico and Peru, it was mainly silver (85-99%). In Russia at the beginning of the 19th century. new deposits of gold began to be developed in the Urals and Siberia, and for three decades the country occupied first place in the world in its production. In the middle of the 19th century. rich gold deposits were discovered in the USA (California) and Australia, in the 1880s. - in the Transvaal (South Africa). The development of capitalism and the expansion of intercontinental trade increased the demand for money metals, and although gold production increased, in all countries, along with gold, silver was still widely used as money. At the end of the 19th century. there was a sharp decline in the cost of silver due to the improvement of methods for its extraction from polymetallic ores. The growth of world gold production, and especially its influx into Europe and the United States from Australia and Africa, hastened the ousting of depreciated silver and created the conditions for the transition of most countries to monometallism (gold) in its classic form of the gold coin standard. The first to go over to gold monometallism at the end of the 18th century. United Kingdom. To the head of the 20th century. the gold currency has established itself in most countries of the world.

Reflecting the relations of people in the conditions of spontaneous commodity production, the power of wealth appears on the surface of phenomena as the relation of things, seems to be a natural intrinsic property of wealth and gives rise to gold and money fetishism. . The passion for the accumulation of gold riches grows endlessly, pushes one to monstrous crimes. The power of the state increases especially under capitalism, when labor power becomes a commodity. Education under capitalism of the world market expanded the sphere of circulation of gold and made it world money.

During the general crisis of capitalism, the gold standard is undermined. In the internal circulation of the capitalist countries, paper money and banknotes irredeemable for gold are becoming dominant. The export of gold and its purchase and sale are limited or prohibited altogether. In this regard, gold ceases to perform the functions of a medium of circulation and a means of payment, but, acting ideally as a measure of value, and also preserving the importance of a means of forming treasures and world money, it remains the basis of monetary systems and the main means of final settlement of mutual monetary claims and obligations of capitalist countries. ... The size of gold reserves is an important indicator of the stability of capitalist currencies and the economic potential of individual countries. . The purchase and sale of gold for industrial consumption, as well as for private saving (accumulation), is carried out in special gold markets. The loss of gold from the free interstate market circulation caused a reduction in its share in the currency system of the capitalist world and, above all, in the foreign exchange reserves of the capitalist countries (from 89% in 1913 to 71% in 1928, 69% in 1958, and 55% in 1969). An increasingly significant part of the newly mined gold is supplied for thezavration and industrial use (in the modern chemical industry, for rocketry, and space technology). Thus, in 1960-70, the private use of gold increased by 3.3 times, its industrial and jewelry use almost 2.3 times, and the gold reserves of the capitalist countries remained practically at the same level ($ 41 billion). (On gold mining in capitalist countries, see Art. Gold mining industry.)

Under the conditions of a socialist economy, gold is also a universal equivalent, acting as a measure of value and a scale of prices. From January 1, 1961, the gold content of the Soviet ruble was set at 0.987412 G net gold. The same amount of gold is the basis for the transferable ruble, the international socialist currency of the CMEA member countries. In the world socialist market, gold performs the function of world money.

Lit .: Mikhalevsky F. I., Gold during the World Wars, [M.], 1945; his, Gold in the system of capitalism after the Second World War, M., 1952; Borisov S.M., Gold in the economy of modern capitalism, M., 1968.

It is also a very beautiful and rather mysterious metal of a noble yellow color. It has both material and historical value.

"Golden" story

This story begins from ancient times, because it was this material that gave rise to a new era - the era of metals. People then extolled him for his unusual "sunny" color. It was believed that only people of noble blood could possess this metal. It was prestigious, because gold has always played an important material role. It could be exchanged for anything, and women decorated their hair and clothes with it. In addition to the pluses, there were also minuses. Gold is wealth, and wealth has often led to unrest and wars. The desire for independence was stronger than humanity, and people died. A lot of people.

Properties of gold

Gold, despite its elegance and beauty, is a very heavy metal. It is not exposed to virtually any chemical attack, which earned it the title of "noble metal". It is very soft and ductile, so the number of different types of gold products is constantly growing, but excessive fragility does not allow using it in its pure form - only with the addition of silver or copper. By the way, their color directly depends on the percentage of these materials in the product. Good thermal conductivity also allows the use of gold in the manufacture of various types of devices.

Mining

Mining gold is not easy, because regardless of the fact that it is the most popular metal, it is also low in concentration. That is, a negligible amount of it falls on a large space. For example, there is a lot of this rock in the World Ocean, but it is so much scattered over the ocean floor that it is almost impossible to get it. The same goes for the earth's crust. But there are also rich deposits. The main thing is to know where to look. The types of gold mined also directly depend on the place of production. In the ground, the pieces of gold are crystal-like, and those closer to the water are round.

At all times, gold mining has been a very profitable business, but, in fact, there is not so much of it.

This metal, which conquered the earth and became one of the most important metals, will never lose its value. People have tamed him. We learned how to mix and change, make beautiful things and exchange for useful ones. He will always remain rich in metal and noble.

If this message is useful to you, it's good to see you.

Gold, together with silver and six more platinum group metals, are called noble, or precious, metals. What do these definitions mean? Gold is very reluctant to combine with chemical elements other than metals. The simplest example is interaction with oxygen: after all, base metals in this case are oxidized, and gold retains its appearance and structure. It is for these qualities that the yellow metal has received the definition of "noble". The rarity of gold in nature, its durability and beauty allowed it to receive the status of a precious metal as well. What are the main properties of gold?

Characterization of the physical properties of the metal

Gold is one of the heaviest metals known to man. The metal belongs to the 11th group of the table named after. DI. Mendeleev. Currently, 37 isotopes of the element are known, of which only one can be found in nature - Au197.

Gold as a chemical element has been known since ancient times. The description of the appearance of the metal and its properties were of interest to many scientists belonging to different eras of human history. Gold is the only metal that has a beautiful yellow color initially. In its pure form, the color of the precious metal is bright and warm, it is not for nothing that it has been associated with the sun for centuries.

The density of gold is 19.32 g / cm3; only platinum, osmium, rhenium and iridium have an even higher density. Imagine a golden cube with an edge of 1 meter - its weight will be 19.32 tons. The weight of the same cube of iron will be three times less - about 7 880 kg.

Gold melts at a temperature of 1064.43 ° C - with further heating it begins to volatilize, the boiling point is at 2947 ° C. In the molten state, the color of the metal changes from yellow to pale greenish.

The hardness of gold on the Mohs scale is only 2.5-3.0; in its pure form, the metal is soft. That is why precious metal is rarely used in its pure form: to increase its hardness, it is alloyed with other elements - silver, copper, palladium. Many people, when watching videos of a historical nature or reading books, noticed that often the heroes try gold "to the teeth." This action helped to reveal the deception: there was a tooth mark on the gold coins; on the counterfeit ones, due to the presence of other elements in the composition, such a mark cannot be left.

Gold has been used in all ages for the manufacture of various products - jewelry, dishes, figurines. This use of metal is provided by two of the most important properties of the metal: ductility and ductility.

The yellow metal differs from all others in the greatest malleability. It can be forged without heating into thin sheets up to 0.1 microns thick. Even in such a “rolled” state, gold will retain both its color and its main properties. An example of this use of metal is gold leaf to cover church domes. The increased plasticity and ductility of the precious metal is also used for the benefit of the industry: the thinnest wires for microcircuits are stretched from gold.

The physical properties of gold provide the metal with wide application in the field of microelectronics. The metal is characterized by low resistance, good thermal conductivity and resistance to oxidation processes. The ability of a precious metal to reflect infrared light is used in the glazing of high-rise buildings, in the manufacture of glasses for ships, aircraft and helicopters, visors for astronauts' helmets.

Due to its physical properties, the yellow metal lends itself easily to a wide variety of treatments, including polishing and soldering. All these qualities, along with easy entry into alloys with other metals, have allowed gold from ancient times to occupy a leading position as the main precious metal and raw material for most jewelry.

Characterization of the chemical properties of the metal

The chemical designation of the yellow metal is Au, an abbreviation for "aurum", which means "shining dawn" from Latin. Gold is classified as an inert substance. Under standard conditions, it does not react with natural substances, the only exception is amalgam, a compound of gold and mercury.

The chemical properties of gold exclude the dissolution of the metal in acids and alkalis. This can be done only in aqua regia, which is a mixture of nitric and hydrochloric acids, and always in a concentrated form. In the photo of the works of alchemists of different times, it can be seen that this reaction was accompanied by a drawing of a lion devouring the solar disk.

Gold can be dissolved in liquid bromine and an aqueous solution of cyanide, but always in the presence of oxygen. The metal slowly dissolves in chlorine and bromine water, in a solution of iodine in potassium iodide. As the temperature rises, the ability of gold to react with other compounds increases: it can be dissolved in selenic acid. The acid in this case must be hot and high in concentration.

The properties of gold encompass the fragility of its compounds, which are very easily restored to pure metal. The same amalgam just needs to be heated to 800 ° C.

At home, practically no substances can react with gold. But do not forget that all jewelry - chains, earrings, bracelets, rings - are made not of pure gold, but of its alloys, where other metals are present. Therefore, it is recommended to exclude interactions of gold items with substances that contain mercury, chlorine and iodine.

The chemical properties of gold and its physical characteristics as a metal are not the only qualities that are actively used by humans. Gold has many other useful properties, it is not in vain that it is actively used in traditional and folk medicine.

Gold for medicinal purposes

The first methods of treatment with yellow metal, as well as its basic physical and chemical properties, were reflected in the writings of ancient scientists and alchemists. Gold was also studied during the Middle Ages; scientific research in this area continues to this day. Scientists from different countries are striving to find new ways to use the precious metal in medicine and industry.

Even in ancient times, gold was considered a remedy for many diseases, a real elixir of life. Our ancestors believed that if gold has power over a person, then it can cure his ailments: remove pain, give strength and vigor, relieve stress, eliminate the emerging symptoms of diseases.

The healing properties of gold include:

  • Removal of inflammation;
  • Improving the course of metabolic processes in the body;
  • Allergy cure;
  • Favorable effect on the nervous system;
  • Stimulating brain activity and improving memory;
  • Increasing the endurance of the human body.

When treating with gold, you do not need to do any special procedures; it is enough to wear jewelry made of this precious metal. Ancient healers believed that gold prolongs life.

The main healing properties of gold are usually used in alternative medicine. Gold jewelry is recommended to be worn by everyone who has problems with the heart, liver, skin diseases, as well as women's problems. The precious metal is capable of killing viruses and harmful microbes, therefore it can serve as an additional preventive measure during the cold flu season.

The beneficial properties of solar metal allow folk healers to recommend wearing gold for:

  • Energy supply of the body;
  • Gaining self-confidence;
  • Protection from the evil eye and damage;
  • Maintaining a good mood and quick recovery of strength;
  • Successful fight against depression and stress;
  • Productive work of the brain and memory.

The use of gold for medicinal purposes may not be suitable for everyone: some people have an individual reaction to the metal.

Those who like to wear a lot of massive yellow metal jewelry need to assess whether they are harmful to the body. The properties of gold, aimed at helping a person, may not be useful at all in some cases. In the presence of sensitivity to metal, hair growth may worsen, depression may appear, or a bad mood may simply prevail, tooth decay may begin, internal organs malfunction, or simply an allergy on the skin is observed. In such situations, the use of gold jewelry must be strictly limited.

A little about the magic of gold

Gold is considered a solar metal, a very powerful and powerful element. The magical properties of gold, like the metal of the Sun, affect strong people who have masculine signs in the cosmogram. According to the signs of the zodiac, the precious metal is recommended for constant wearing for Lions, Taurus and Aries, according to your health, you can wear gold jewelry for Sagittarius, Aquarius, Scorpio, Gemini, for other signs, wearing gold should be episodic.

Gold brings wealth. The magical characteristic of metal testifies to the attraction of new money to it, to endowing a person with courage and courage, which are necessary to achieve all the goals set for oneself.

The sun-shaped medallion of gold has long been considered talismans for those who work underground. It allows you to maintain good spirits, restore physical strength, and also protects against landslides and other misfortunes. A precious metal medallion worn in the solar plexus area performs a protective function against any love spell.

For those who want to experience gold and its magical properties of metal, it is necessary not only to wear precious jewelry, but also to believe in their effect. By gaining self-confidence, you will be able to realize all your goals and dreams, which until recently seemed unattainable.

The most different properties of gold - physical, chemical, medicinal - determine its value in human society and the demand for metal in the modern world. There has been a deficit on the precious metal market for many years: supply is much lower than demand. Gold, the technical analysis of which shows a decline in sales, is constantly growing in price, but the extraction of the metal continues to decline from year to year. Compensation for the shortage of metal, which, due to its characteristics, is in demand not only in the field of investment and jewelry, but is also widely used in industrial production, occurs only through the melting and reuse of the yellow metal.

December 15th, 2013

Gold ... Yellow metal, a simple chemical element with atomic number 79. The object of desire of people at all times, a measure of value, a symbol of wealth and power. Bloody metal, spawn of the devil. How many human lives were lost for the sake of possession of this metal !? And how many more will be destroyed?

Unlike iron or, for example, aluminum, there is very little gold on Earth. Throughout its history, mankind has mined gold as much as it mines iron in one day. But where did this metal come from on Earth?

It is believed that the solar system was formed from the remnants of a supernova that exploded in ancient times. In the bowels of that ancient star, there was a synthesis of chemical elements heavier than hydrogen and helium. But in the bowels of stars, elements heavier than iron cannot be synthesized, and therefore, gold could not be formed as a result of thermonuclear reactions in stars. So where did this metal come from in the universe at all?

It looks like astronomers can now answer this question. Gold cannot be born in the depths of stars. But it can be formed as a result of grandiose cosmic catastrophes, which scientists routinely call gamma-ray bursts (GW).

Astronomers closely watched one such gamma ray burst. The observational data give serious enough reason to believe that this powerful burst of gamma radiation was produced by the collision of two neutron stars - dead star cores that died in a supernova explosion. In addition, the unique glow that persisted at the site of the GW for several days indicates that a significant amount of heavy elements, including gold, were formed during this catastrophe.

“We estimate that the amount of gold produced and ejected into space during the merger of two neutron stars could be more than 10 lunar masses,” study lead author Edo Berger of Harvard Smithsonian Astrophysical Center (CfA) said during a CfA press conference. in Cambridge, Massachusetts.

A gamma ray burst (GW) is a burst of gamma rays from an extremely energetic explosion. Most GWs are found in very distant regions of the Universe. Berger and his colleagues studied the object GRB 130603B, located at a distance of 3.9 billion light years. This is one of the closest GWs seen so far.

There are two types of GWs - long and short, depending on how long the gamma ray burst lasts. The duration of the GRB 130603B flare recorded by the NASA Swift satellite was less than two tenths of a second.

Although the gamma radiation itself disappeared quickly, GRB 130603B continued to shine in infrared rays. The brightness and behavior of this light did not match the typical afterglow that occurs when accelerated particles bombard the surrounding matter. The glow from GRB 130603B behaved as if it was coming from decaying radioactive elements. The neutron-rich material ejected from the collision of neutron stars can turn into heavy radioactive elements. The radioactive decay of such elements generates infrared radiation typical of GRB 130603B. This is exactly what astronomers have observed.

According to the group's calculations, during the explosion, substances with a mass of about one hundredth of the solar mass were ejected. And some of that stuff was gold. Having roughly estimated the amount of gold formed during this GW, and the number of such explosions that occurred in the entire history of the Universe, astronomers came to the assumption that all gold in the Universe, including on Earth, may have been formed during such gamma-ray bursts. ...

Here's another interesting but terribly controversial version:

As the Earth formed, molten iron descended down to its center to form its core, taking with it most of the planet's precious metals such as gold and platinum. In general, there are enough precious metals in the core to cover them with a layer of four meters thick the entire surface of the Earth.

The transfer of gold to the core should have deprived the outer part of the Earth of this treasure. However, the abundance of noble metals in the silicate mantle of the Earth exceeds the calculated values ​​by tens and thousands of times. The idea has already been discussed that this super-abundance is due to the catastrophic meteor shower that overtook the Earth after the formation of its core. The entire mass of meteorite gold thus entered the mantle apart and did not disappear deep inside.

To test this theory, Dr. Matthias Willbold and Professor Tim Elliot of the Bristol Isotope Group at the School of Earth Sciences analyzed rocks collected in Greenland by Oxford University professor Stephen Murbat, which are about 4 billion years old. These ancient stones provide a unique picture of the composition of our planet shortly after the formation of the core, but before the alleged meteorite bombardment.

Then scientists began to study the content of tungsten-182 in meteorites, which are called chondrites - this is one of the main building materials of the solid part of the solar system. On Earth, unstable hafnium-182 decays to form tungsten-182. But in space, due to cosmic rays, this process does not occur. As a result, it became clear that samples of ancient rocks contain 13% more tungsten-182 compared to younger rocks. This gives geologists reason to assert that when the Earth already had a hard crust, about 1 million trillion (10 to the 18th power) tons of asteroid and meteorite matter fell on it, which had a lower content of tungsten-182, but much more than in the earth's crust, the content of heavy elements, in particular gold.

Being a very rare element (there is only about 0.1 milligram of tungsten per kilogram of rock), like gold and other precious metals, it had to enter the core at the time of its formation. Like most other elements, tungsten is subdivided into several isotopes - atoms with similar chemical properties but slightly different masses. By isotopes, one can confidently judge the origin of matter, and mixing of meteorites with the Earth should have left characteristic traces in the composition of its tungsten isotopes.

Dr. Willbold has noticed a 15 ppm reduction in the isotope of tungsten-182 in modern rock compared to the Greenland.

This small but significant change is in excellent agreement with what was required to be proved - that the surplus of available gold on Earth is a positive side effect of meteorite bombardment.

Dr. Willbold says: “Extracting tungsten from stone samples and analyzing its isotopic composition with the required accuracy was extremely difficult given the small amount of tungsten present in the stones. In fact, we became the first laboratory in the world to successfully carry out measurements of this level. "

The fallen meteorites mixed with the earth's mantle in the course of giant convection processes. The maximum challenge for the future is to find out the duration of this mixing. Subsequently, geological processes shaped the continents and led to the concentration of precious metals (as well as tungsten) in ore deposits that are mined today.

Dr. Willbold continues, "Our findings show that most of the precious metals on which our economies and many of our key manufacturing processes are based, were brought to our planet by a lucky coincidence, when the Earth was covered with about 20 quintillion tons of asteroid material."

Thus, we owe our gold reserves to the present flow of valuable elements that ended up on the planet's surface due to the massive asteroid “bombardment”. Then, during the development of the Earth over the past billions of years, gold entered the cycle of rocks, appearing on its surface and again hiding in the depths of the upper mantle.

But now the way to the core is closed for him, and a large amount of this gold is simply doomed to end up in our hands.

Merging neutron stars

And another scientist's opinion:

The origin of gold remained completely unclear, because, unlike lighter elements such as carbon or iron, it cannot form directly inside the star, admitted one of the researchers at the Edo Berger Center.

The scientist came to this conclusion by observing gamma-ray bursts - large-scale cosmic emissions of radioactive energy caused by the collision of two neutron stars. The gamma ray burst was spotted by NASA's Swift spacecraft and lasted just two tenths of a second. And after the explosion, a glow remained, which gradually disappeared. The glow from the collision of such celestial bodies indicates the release of a large amount of heavy elements, experts say. And proof that heavy elements were formed after the explosion is infrared light in their spectrum.

The fact is that neutron-rich substances ejected during the collapse of neutron stars can generate elements that undergo radioactive decay, while emitting a glow mainly in the infrared range, Berger explained. “And we believe that a gamma-ray burst throws out about one-hundredth of the solar-mass material, including gold. Moreover, the amount of gold produced and ejected during the merger of two neutron stars can be comparable to the mass of 10 moons. And the cost of such a quantity of precious metal would be equal to 10 octillion dollars - that's 100 trillion squared.

For reference, an octillion is a million septillion, or a million to the seventh power; a number equal to 1042 and written in decimal as one followed by 42 zeros.

Also today, scientists have established the fact that almost all gold (and other heavy elements) on Earth is of cosmic origin. Gold, it turns out, fell on Earth as a result of an asteroid bombardment that occurred long ago after the solidification of the planet's crust.

Almost all heavy metals "drowned" in the Earth's mantle at the earliest stage of the formation of our planet, they formed a solid metal core in the center of the Earth.

Alchemists of the 20th century

Back in 1940, American physicists A. Sherr and K. T. Bainbridge from Harvard University began to irradiate the elements adjacent to gold with neutrons - mercury and platinum. And quite expectedly, having irradiated mercury, they obtained isotopes of gold with mass numbers 198, 199, and 200. Their difference from natural natural Au-197 is that isotopes are unstable and, emitting beta rays, within a few days at the most, again turn into mercury with mass numbers numbers 198,199 and 200.

But it was still great: for the first time, a person was able to independently create the necessary elements. It soon became clear how one could get real, stable gold-197 at all. This can be done using only the isotope mercury-196. This isotope is quite rare - its content in ordinary mercury with a mass number of 200 is about 0.15%. It must be bombarded with neutrons in order to obtain unstable mercury-197, which, having captured an electron, will turn into stable gold.

However, calculations have shown that if we take 50 kg of natural mercury, then it will contain only 74 grams of mercury-196. For transmutation into gold, the reactor can produce a neutron flux of 10 to the 15th power of neutrons per square meter. cm per second. Taking into account that 74 g of mercury-196 contains about 2.7 per 10 in the 23rd power of atoms, it would take four and a half years for the complete transmutation of mercury to gold. This synthetic gold is infinitely more expensive than gold from the earth. But this meant that giant neutron fluxes were also needed to form gold in space. And the explosion of two neutron stars explained everything.

And more details about gold:

German scientists have calculated that in order for the present volume of precious metals to be brought to the Earth, only 160 metallic asteroids, each about 20 km in diameter, were needed. Experts note that the geological analysis of various noble metals shows that they all appeared on our planet at about the same time, however, on the Earth itself, there were no and there are no conditions for their natural origin. This is what prompted specialists to the cosmic theory of the appearance of noble metals on the planet.

The word "gold", according to linguists, comes from the Indo-European term "yellow" as a reflection of the most prominent characteristic of this metal. This fact is confirmed by the fact that the pronunciation of the word "gold" in different languages ​​is similar, for example Gold (in English), Gold (in German), Guld (in Danish), Gulden (in Dutch), Gull ( in Norwegian), Kulta (in Finnish).

Gold in the bowels of the earth


The core of our planet contains 5 times more gold than all other rocks available for development combined. If all the gold of the Earth's core poured onto the surface, it would cover the entire planet with a layer half a meter thick. Interestingly, about 0.02 milligrams of gold is dissolved in every liter of water of all rivers, seas and oceans.

It has been determined that for the entire time of the extraction of the precious metal, about 145 thousand tons were extracted from the bowels (according to other sources, about 200 thousand tons). Gold production is growing from year to year, but the main growth came in the late 1970s.

The purity of gold is determined in various ways. Carat (spelled "Karat" in the US and Germany) was originally a unit of mass based on the seeds of the "carob tree" (consonant with the word "carat") used by ancient Middle Eastern traders. The carat is mainly used today when measuring the weight of gemstones (1 carat = 0.2 grams). Gold purity can also be measured in carats. This tradition dates back to ancient times, when carat in the Middle East became the yardstick for the purity of gold alloys. The British carat of gold is a non-metric unit for evaluating the gold content in alloys, equal to 1/24 of the mass of the alloy. Pure gold is 24 carats. The purity of gold today is also measured by the concept of chemical purity, that is, thousandths of pure metal in the mass of the alloy. So, 18 carats is 18/24 and in terms of thousandths corresponds to the 750th sample.

Gold mining


As a result of natural concentration, approximately only 0.1% of all gold contained in the earth's crust is available, at least theoretically, for mining, but due to the fact that gold occurs in its native form, shines brightly and is easily noticeable, it became the first metal with whom the person met. But natural nuggets are rare, so the most ancient method of mining the rare metal, based on the high density of gold, is the washing of gold-bearing sands. "The extraction of flushed gold requires only mechanical means, and therefore it is not surprising that gold was known even to savages in the most ancient historical times" (DI Mendeleev).

But there are almost no rich gold placers left, and already at the beginning of the 20th century, 90% of all gold was mined from ores. Nowadays, many gold placers are practically depleted, therefore, mainly ore gold is mined, the extraction of which is largely mechanized, but production remains difficult, since it is often located deep underground. In recent decades, the share of more cost-effective open source mining has steadily increased. It is economically profitable to develop a deposit if a ton of ore contains only 2-3 g of gold, and if the grade is more than 10 g / t, it is considered rich. It is significant that the costs of prospecting and exploration for new gold deposits account for 50 to 80% of all exploration costs.

Now the largest supplier of gold to the world market is South Africa, where the mines have already reached 4 kilometers depth. South Africa is home to the world's largest Vaal Reefs mine at Klexdorp. South Africa is the only state where gold is the main product of production. There it is mined at 36 large mines, which employ hundreds of thousands of people.

In Russia, gold is mined from ore and placer deposits. The opinions of researchers differ about the beginning of its extraction. Apparently, the first domestic gold was mined in 1704 from the Nerchinsk ores together with silver. In the following decades, at the Moscow Mint, gold was isolated from silver, which contained some gold as an impurity (about 0.4%). So, in 1743-1744. “From gold found in silver smelted at the Nerchinsk factories”, 2820 ducats were made with the image of Elizabeth Petrovna.

The first gold placer in Russia was discovered in the spring of 1724 by the peasant Erofei Markov in the Yekaterinburg region. Its operation began only in 1748. The mining of the Ural gold was slowly but steadily expanding. At the beginning of the 19th century, new gold deposits were discovered in Siberia. The discovery (in the 1840s) of the Yenisei deposit brought Russia to the first place in the world in gold mining, but even before that, local Evenki hunters made bullets from gold nuggets for hunting. At the end of the 19th century, Russia mined about 40 tons of gold per year, of which 93% was alluvial gold. All in all, in Russia before 1917, according to official data, 2754 tons of gold were mined, but according to experts - about 3000 tons, and the maximum was in 1913 (49 tons), when the gold reserve reached 1684 tons.

With the discovery of rich gold-bearing areas in the United States (California, 1848; Colorado, 1858; Nevada, 1859), Australia (1851), South Africa (1884), Russia lost its leadership in gold mining, despite the fact that new fields were commissioned, mainly in Eastern Siberia.
Gold mining was carried out in Russia using a semi-handicraft method, mainly alluvial deposits were developed. Over half of the gold mines were in the hands of foreign monopolies. At present, the share of alluvial mining is gradually decreasing, amounting to a little over 50 tonnes by 2007. Less than 100 tons are mined from ore deposits. Final processing of gold is carried out at refineries, the leading of which is the Krasnoyarsk Non-Ferrous Metals Plant. It accounts for refining (purification from impurities, obtaining metal with a sample of 99.99%) about 50% of mined gold and most of the platinum and palladium mined in Russia.

... And for example you know The original article is on the site InfoGlaz.rf The link to the article this copy was made from is

There is no person who has not seen gold in jewelry. The bright yellow metal has been known to people for thousands of years. However, in nature, gold has many faces. The size of its particles ranges from microns to tens of centimeters, the color, due to impurities, is not always yellow. There are several minerals similar to gold in appearance. It is not for nothing that there is a saying “not all that glitters is gold”. To successfully find gold, navigate its value, not to be confused with similar minerals, you need to know the properties of gold, where and how it occurs in nature.

Physical properties of gold
The color of gold is bright yellow if there are no impurities in it. But pure gold (and even then not entirely) is almost exclusively in bank bullions. Natural gold and jewelry always contain impurities of silver, copper, etc., that is, in fact, we always deal with alloys of gold with other metals. Natural gold color can be influenced by particle size. For example, the gold from the Baleyskoye deposit in the Chita region is described as follows: “Gold is usually found in veins in the form of tiny particles. These particles sometimes accumulate, giving loose aggregates and clusters visible to the naked eye. The appearance of these clusters is such that the observer who sees them for the first time does not recognize gold in them. These are gray-green spots of a very unattractive appearance with a dull sheen or no sheen at all. This kind of gold is called "green" gold. Much less common is the so-called "yellow" gold, somewhat different in appearance and composition from "green". The ratio of the amount of "green" to "yellow" is approximately 20: 1.

In jewelry, gold is sometimes called alloys in which the actual gold is less than 40%. The alloy known as "white gold" is an alloy of gold and palladium. One tenth of palladium gives the ingot a steel-white hue. Platinum turns gold white even more intensely than palladium. Nickel also makes it possible to obtain white gold alloys with a subtle yellow tint. Jewelry with diamonds is made of white gold. Such a frame perfectly reflects the brilliance of the stones and, as if, additionally illuminates them. Compared to yellow, white gold is more resistant to atmospheric influences. Thus, the color of the alloys depends on the amount and composition of impurities (Table 1).

Table 1. Gold color depending on the amount and composition of impurities

Share of gold,%

The proportion of impurities,%

Main composition of impurities

Alloy color

100,0

yellow

96,0

Copper

yellow

Copper

Red

75,0

25,0

copper, silver, nickel; copper, silver

yellow

nickel, zinc, copper; palladium, silver, copper

White

50,0 - 58,0

42-50

copper, silver

Red

silver, copper

yellow

silver, copper

green

37,5

62,5

copper, silver

Red

silver, palladium, copper

pink

Gold is a very soft metal, its hardness is 2.5-3.0 on a 10-point hardness scale (Mohs scale). On this scale, the hardest substance is diamond. Its hardness is 10. The softest substance is chalk. Its hardness is 1. The hardness of glass is 5, that of good steel is 4.5. In the field, hardness is checked primarily with a knife. Its tip is carried over the surface of the mineral under study. If the knife leaves a scratch, then the hardness is less than 5. Gold, having a hardness of 2.5-3.0, is not only easily scratched, but also cut with a knife with considerable effort. You can leave a mark on it even if you bite hard with your teeth. They used to taste gold coins. It is impossible to make a mark with teeth on fake copper coins, but you can put a mark on a gold coin with strong teeth. The hardness test is an important test for distinguishing gold from similar colored metals or minerals.

Gold is easy to polish and highly reflective. The sun's rays can perfectly pass through very thin sheets of gold, while their thermal part will be reflected. For this reason, thin layers of gold are used for tinted glass in modern skyscrapers in hot climates. This saves the energy needed to keep the interior cool during the hot summer months. Similar thin layers of gold are also used in protective helmets for astronauts to reflect large infrared rays in outer space.

Gold has an exceptional ability to spray, give particles comparable to the wavelength of light, be carried away in tons in the form of the smallest dust in rivers, scatter on the floors, walls and furniture of gold-alloy laboratories and disappear from bank exchange due to the abrasion of coins. With gold circulation, from 0.01 to 0.1% of the weight of the coin was lost annually.

The famous Austrian geologist Süss saw the impending "golden famine" in these exceptional properties of gold and pointed out the need to carefully address the issue of gold circulation as the basis of the world economy. Perhaps Suess's fears were premature, but their significance remained in force, although the pace of approaching golden exhaustion did not materialize.

Gold has extremely high ductility (ductility) and malleability (forged to a thickness of 8 ∙ 10 -5 mm), i.e. from one gram of gold, you can get a sheet of foil with an area of ​​up to 1m 2. Due to its high ductility, gold can be crushed, bent, squeezed, compressed, gold can be given various shapes without breaking into pieces. In fact, yellow metal can be crushed to translucency, as thin as a sheet of paper, and still beautiful and shiny. The production of thin-leaf (leaf) gold allows it to cover the domes of churches, to decorate the palace halls.

A wire 2610 m long can be drawn from one gram of gold. The resulting thread is very thin (2 ∙ 10 -6 mm in diameter), which is necessary for today's electronic industry, where it is necessary to create electrical circuits in very small chips. Due to its high electrical conductivity and oxidation resistance, gold is in great demand in the electronics industry. Nowadays it's no surprise to find gold in devices such as televisions, mobile phones, calculators, not to mention more sophisticated electronics.

The high malleability of gold is another sign that distinguishes gold from similar minerals. For example, if you put a particle of gold on a hard stone and hit it with a hammer, it will flatten, and a piece of yellow pyrite will crumble into small particles.

The melting point of gold is 1063˚C, the boiling point is 2947˚C. Molten gold is pale green in color. Greenish-yellow gold pairs. All metals that make up the alloy with gold lower its melting point. When gold and its alloys are heated above the melting temperature, gold begins to volatilize, and its volatility is higher, the higher the temperature. The volatility of gold also increases significantly when the alloy contains other metals with volatile properties, for example, zinc, arsenic, antimony, tellurium, mercury, etc. Alloys in their properties are not similar to those metals of which they formed. So, for example, an alloy of gold with silver has a much higher hardness than gold and silver, but it does not have their malleability and ductility. The same is given by an admixture of copper.

Gold has another distinctive quality that is perhaps the most important to the prospector (other than price) - the density of the gold. Its density - 19.3 g / cm 3 - means that it weighs 19.3 times more than an equal volume of pure water. Only some metals of the platinum group have a higher density (indium - 22.6 g / cm 3). A particle of gold is 2.5 times heavier than a similar particle of silver, and about 8 times heavier than a piece of quartz, which is usually found next to gold. 1 kg of gold can be represented as a cube with an edge of 37.3 mm or a ball with a diameter of 46.2 mm. Half a glass of gold sand extracted from a placer deposit also weighs about a kilogram. The high density of gold is the property most commonly used to extract it from rock.

The density of native gold is somewhat lower than that of chemically pure gold, and, depending on the impurities in it of silver and copper, ranges from 18 to 18.5.

Tab. 2. The most important physical properties and diagnostic features of gold

Properties

Meaning

Colour

yellow

Line color (on unglazed porcelain plate)

yellow

Shine

metal

Mohs hardness

2,5-3,0

Density at 20ºC

19.32 g / cm 3

Temperature, melting, deg. C

Boiling

1063

2947

Specific thermal conductivity at a temperature of 0ºC, W / (m ∙ K)

311,48

Resistance at temperature 0º, Ohm

2,065∙10 -8

Electrical conductivity in relation to copper,%

Ultimate tensile strength of annealed gold, MPa

100-140

Chemical properties of gold.
Gold (Au, from the Latin Aurum) is a chemical element of the 1st group of the periodic table of the periodic table, atomic number 79. Almost all natural gold consists of the 197 Au isotope. The valence of gold in chemical compounds is usually +1, +3. Over the past centuries, chemists (and before them alchemists) have carried out a huge number of different experiments with gold, and it turned out that gold is not at all as inert as non-specialists think of it. True, sulfur and oxygen, which are aggressive towards most metals (especially when heated), do not affect gold at any temperature. The exception is gold atoms on the surface. At 500-700 ° C, they form an extremely thin, but very stable oxide that does not decompose within 12 hours when heated to 800 ° C. This can be Au 2 O 3 or AuO (OH). Such an oxide layer is found on the surface of native gold grains.

Gold does not react with hydrogen, nitrogen, phosphorus, carbon, and when heated, halogens form compounds with gold: AuF 3, AuCl 3, AuBr 3 and AuI. It is especially easy, already at room temperature, to react with chlorine and bromine water. Only chemists are found with these reagents. In everyday life, the danger to gold rings is an iodine tincture - an aqueous-alcoholic solution of iodine and potassium iodide:

2Au + I 2 + 2KI ® 2K.

Alkalis and most mineral acids have no effect on gold. One of the ways to determine the authenticity of gold is based on this. All the crushed metal is poured into a porcelain cup, where nitric acid is poured in an amount sufficient to cover the entire metal. A cup with acid and metal, with continuous stirring with a glass rod, is heated on a stove to a boil. If this does not dissolve the metal and the evolution of gas bubbles, then the metal is gold. A mixture of concentrated nitric and hydrochloric acids ("aqua regia") easily dissolves gold:

Au + HNO 3 + 4HCl ® H + NO + 2H 2 O.

After careful evaporation of the solution, yellow crystals of the complex hydrochloric acid HAuCl 4 · 3H 2 O are released. The Arab alchemist Geber, who lived in the 9-10th century, knew the royal vodka capable of dissolving gold. It is less known that gold dissolves in hot concentrated selenic acid:

2Au + 6H 2 SeO 4 ® Au 2 (SeO4) 3 + 3H 2 SeO 3 + 3H 2 O.

In concentrated sulfuric acid, gold dissolves in the presence of oxidizing agents: iodic acid, nitric acid, manganese dioxide. In aqueous solutions of cyanides, when oxygen is available, gold dissolves to form very strong dicyanoaurates:

4Au + 8NaCN + 2H 2 O + O 2 ® 4Na + 4NaOH;

this reaction underlies the most important industrial method for extracting gold from ores - cyanidation.

Affect gold and melts from a mixture of alkalis and alkali metal nitrates:

2Au + 2NaOH + 3NaNO 3 ® 2Na + 2Na 2 O,

sodium or barium peroxides: 2Au + 3BaO 2 ® Ba 2 + 3BaO,

aqueous or ethereal solutions of higher chlorides of manganese, cobalt and nickel:

3Au + 3MnCl 4 ® 2AuCl 3 + 3MnCl 2,

thionyl chloride: 2Au + 4SOCl 2 ® 2AuCl 3 + 2SO 2 + S2Cl 2, some other reagents.

The properties of finely crushed gold are interesting. When gold is reduced from highly dilute solutions, it does not precipitate, but forms intensely colored colloidal solutions - hydrosols, which can be purple-red, blue, violet, brown and even black. So, when a reducing agent is added to a 0.0075% solution of H (for example, a 0.005% solution of hydrochloric acid hydrazine), a transparent blue gold sol is formed, and if a 0.005% solution of potassium carbonate is added to a 0.0025% solution of H , and then add a solution of tannin dropwise while heating, then a red transparent sol is formed. Thus, depending on the degree of dispersion, the color of gold changes from blue (coarse sol) to red (fine sol).

With a sol particle size of 40 nm, the maximum of its optical absorption falls on 510-520 nm (red solution), and with an increase in particle size to 86 nm, the maximum shifts to 620-630 nm (blue solution). The reduction reaction with the formation of colloidal particles is used in analytical chemistry to detect small amounts of gold.

When gold compounds are reduced with tin chloride in weakly acidic solutions, an intensely colored dark purple solution of the so-called golden cassia purple is formed (it is named after Andreas Cassius, a glassmaker from Hamburg who lived in the 17th century). Cassian purple, injected into a molten glass mass, produces a magnificently colored ruby ​​glass, the amount of gold spent in this is negligible. Cassiev purple is also used for painting on glass and porcelain, giving various shades when calcined - from slightly pink to bright red.

In geological processes, the mobility of gold is associated with aqueous solutions that have a high temperature (hundreds of degrees) and are under high pressure. In this case, gold can be in the form of various simple and mixed complexes: hydroxyl, hydroxychloride, hydrosulfide. In low-temperature hydrothermal conditions, as well as in the biosphere, gold migration is possible in the form of soluble organometallic complexes.

Under normal natural conditions, gold is resistant to various types of mineral waters and atmospheric corrosion. Gold particles remain virtually unchanged over time. Gold items made thousands of years ago remain virtually unchanged in land and sea water. Over time, they not only do not lose their value, but become more expensive. This stability gives reason to classify gold as a group of noble metals.

Gold content.
The quantitative content of chemically pure gold (by weight) in a natural solid solution or alloy (product) is expressed by breakdown. In international practice, metric (in most countries, including Russia) and carat sampling systems are used.

With the metric system, the metal content is determined by the number of its units in 1000 units of the ligature mass of the solution (alloy), with the carat in 24 units. Until 1927, in the USSR, as well as in pre-revolutionary Russia, a spool sample system operated, in which the gold content was determined by the number of spools in a pound of ligature mass (1 Russian pound = 409.5 g = 96 spools; 1 spool = 4.27 g = 96 lobes; 1 lobe = 44.4 mg).

In the metric system, chemically pure gold corresponds to the 1000th standard, and a solid solution (alloy), for example, 750th standard, contains 750 parts of chemically pure gold and 250 parts of impurities (ligature), or 75.0% gold and 25, 0% impurities.

The calculation establishes the relationship and translation of various sample systems. For example, the 450th metric standard of a product (alloy) corresponds to:

450/1000 ´ 96 = 43.2 spool

and 550/1000 ´ 24 = 10.8 carat samples.

Native gold has different fineness (most often 940-900, 890-740, 680-600 and very rarely 550). For the production of jewelry and household products, gold alloys of various fineness are usually used, since gold in its pure form is too soft and easily abraded.

Jewelry alloys due to the addition of ligature non-ferrous metals (copper, silver, less often nickel, palladium, zinc, cadmium, etc.) are given the properties required for machining and the desired color. Table 3 shows the alloys most often used for the production of jewelry and the ratio of various designation systems for their samples, common in the former USSR and Russia.

Table 3. Samples and basic composition of the ligature of jewelry gold alloys adopted in the former USSR and the Russian Federation

Sample designation system

metric

spool

carat

1000

750*

583/585*

500*

375*

* Samples of the Russian Federation

Gold in nature.
Gold is found in small quantities in many rocks. Its average content in the lithosphere (Clarke) is 4.3 mg / t.

Gold is found in organisms and plants. There is an assumption that gold has a certain value for the body of animals. In plant ash, gold was first discovered by the French chemist Claude Louis Berthollet in the 18th century. According to modern data, the gold content in some humus soils reaches 0.5 g / t. Plants growing in such areas absorb gold, concentrating it in the root system, stems, trunks and branches. At present, methods of searching for deposits (biogeochemical) have been developed, based on the identification of halos with an increased gold content in plant ash.

A huge amount of gold is contained in the hydrosphere. In all types of fresh waters, its average content is about 3 ∙ 10-9% (0.03 mg / t), but sometimes it is many times higher, for example, in underground waters of gold ore deposits, the gold content reaches about 1 mg / t. One of the methods of prospecting for gold deposits (hydrochemical method) is based on changes in the gold content in groundwater.

In sea waters, the gold content also fluctuates: in the polar seas - 0.05 mg / t, off the coast of Europe - 1-3 ∙ mg / t. The highest concentration of gold is noted in the coastal zone of the United States - up to 16 mg / t, in the waters of the Caribbean Sea - 15-18 mg / t, in the waters of the Dead Sea - up to 50 mg / t.

The oceans are saturated with gold due to its introduction by ground, ground and surface waters, due to the spraying of meteorites, emissions of volcanic substances and a number of other natural sources. French researchers found that the Sicilian volcano Etna every day throws out more than 2.5 kg in the form of small particles, and most of this goes into the ocean. It is estimated that about 3.5 thousand meteorite matter is sprayed into the Earth's atmosphere every year, containing about 18 kg of gold, which is about 18 thousand tons per million years. The entry of gold into the oceans also occurs with river and marine suspensions, as well as in the form of soluble organometallic complexes. Surface and groundwater streams circulating in gold-bearing areas usually contain suspended gold or dissolved gold that can reach the ocean. The transfer of gold by river systems is especially great. Experts calculated that the Amur alone in its waters carries about 8.5 tons of gold into the ocean per year.

The total amount of gold in the waters of the World Ocean is estimated at 25-27 million tons. This is extremely high. For the entire time, mankind has produced about 150 thousand tons. Technologies for extracting gold from oceans are being researched, technical solutions have been patented, but acceptable economic indicators for extracting gold from water have not yet been achieved.

In the earth's crust, gold can be found in solid rock masses - ores or in destroyed rocks - placers. In the first case, it is called ore gold, and in the second, placer gold. Placers are usually found in river valleys, streams or dry ravines and form more or less thick strata, covered with a layer of waste rock, the so-called peat. Zo-loto is found in placers in the form of pieces, scales, grains and dust.

Gold in ore and placer deposits is found mainly in alloys with silver, copper, iron and other metals. In addition to these natural alloys of gold, platinum and rhodium gold are also known, which respectively include platinum and rhodium. Most often, native gold contains from 5 to 30% silver. Relatively rare, but still found in nature, an alloy of gold with 30-40% silver, which is called electrum. Native cuprous gold is quite common in nature, consisting of 74-80% gold, 2-16% silver, 9-20% copper.

Most of all in nature there are gold particles ranging in size from a fraction of a micron to tens of microns. Such particles are called dispersed. They are conventionally divided into coarse and fine (highly dispersed). In coarsely dispersed systems, particles have sizes from 1 μm and more, in finely dispersed systems, from 1 nm to 1 μm (0.001 mm).

Dispersed particles of gold are found in rocks, in water and in plants. Such particles are visible only through an electron microscope; they cannot be weighed on the best microanalytical balance. The calculated mass of a particle with a size of 0.001 mm is only 0.00000001 mg, and the weighing limit of the best microanalytical balance is 0.0001 mg. The number of tiny particles of gold is innumerable. Each gram of gold contains more than 100 billion of these particles. With a huge amount of dispersed particles, their extraction is the most difficult and costly.

Gold grains of the order of 0.01 mm are also extremely abundant in nature. The largest gold grain of this class (0.01 mm) has a mass of about 0.00001 mg and it is also impossible to weigh it on a microanalytical balance. Each gram of gold contains more than 100 million such particles. Despite the fact that gold is finer than 0.01 mm in nature, more than any other, it is predominantly in a dispersed state. Sometimes it is concentrated in the form of inclusions in some minerals (pyrite, arsenopyrite, etc.), but if free gold with a particle size of 0.01-0.1 mm enters the river flow, then it is mainly dispersed. Small light gold grains are freely transported in a suspended state even at low flow rates.

Gold larger than 0.1 mm refers to "gravity", that is, to such that is deposited in water under the influence of gravity and forms accumulations that are beneficial for mining - placer deposits. Gold extracted from placers is often referred to as "golden sand". In fact, the way it is, gold particles are easily poured and they can be poured into a leather bag (they used to carry it in a pocket or bag), gold dust can be poured into a bottle (it is convenient to hide gold in it) or into any container.

Gold grains with a size of 8 mm or more usually weigh more than 1 g and are called nuggets. There are small nuggets (1-10 g), medium (10-100 g), large (100-1000 g), very large (1-10 kg) and giant (more than 10 kg). However, sometimes nuggets are also called gold grains "sharply distinguished in size from other metal particles", and the lower limit of the mass of a nugget is taken to be 0.1 grams.

The largest nugget of gold was found in Australia - "Holterman Plate" (285 kg together with quartz, pure gold 83.3 kg); a nugget of gold “Big Triangle” (36.2 kg) was found in the Urals. Most of the large nuggets have their own names (Table 4).

Tab. 4. The largest nuggets in the world

Year of discovery

Place of find

Weight,

Kg

Assigned name

Source of information

1842

Russia, Ural

36,2

"Big Triangle"

V.V. Danilevsky

1851

Australia, New South Wales

45,3

"Mopeway"

J. Salmon

1857

Australia, Kingower

65,7; 54

"Shiny Barkley"

J. Salmon

1857

Australia, Victoria

Donnoli

V.I.Sobolevsky

1858

Australia, Ballarat

"Desired"

V.I.Sobolevsky

1868

Australia, Ballarat

"Canadian 1st"

J. Salmon, V. I. Sobolevsky

1870

Australia, Victoria

60,7

No

J. Salmon

1870

California

No

J. Salmon

1872

Australia, Sydney area

285/83,2

"Halterman Plate"

V.I.Sobolevsky

1873

California

108,8

No

J. Salmon

1899

Western Australia

45,3

No

J. Salmon

1901

Japan, Hokkaido

"Japanese"

V.I.Sobolevsky

1937

Australia

"Golden Eagle"

From newspapers

1954

USA, Calaveras

72,9

No

J. Salmon

1954

California

36,3

"Oliver Martin"

J. Salmon

1983

Brazil, pair

39,5; 36

No

From newspapers

n.d.

California

88,4

No

J. Salmon

n.d.

Australia

75,4

No

D.S. Newbury

n.d.

Australia, Victoria

44,7

"Lady Hotham"

J. Salmon

XX century

Western China

No

J. Salmon

n.d.

Australia, Victoria

"Canadian 2nd"

V.I.Sobolevsky

n.d.

California

35,6

"Poseidon 2nd"

V.I.Sobolevsky

In recent decades, metal detectors (a type of mine detector) have begun to look for nuggets. The largest nugget found by a metal detector weighs 27.2 kg. It was found in Australia in the state of Victoria by Kevin Hillier on September 26, 1980. The nugget is named "The Hand of Destiny". It measures 47 cm long, 20 cm wide and 9 cm thick, fineness 926. Kevin sold his nugget in 1981 for $ 1,000,000 at the Golden Nugget casino in Las Vegas.

It is difficult to name another metal that would have played a greater role in the history of mankind than gold. At all times, people have tried to take possession of gold at least through crime, violence and war. Starting with primitive man, who adorned himself with golden spangles washed up in the sands of rivers, and ending with a modern industrialist with enormous production, man, in a stubborn struggle, took possession of a part of natural wealth. But this part of gold is insignificant in comparison with the amount of metal sprayed in nature and with the needs and desires of humanity itself. Today, prospecting for gold and its deposits is going on at an ever-increasing pace, at least five million people work in the extraction of gold all over the world, and about three thousand tons of it are mined annually. Nature very carefully preserves its treasures and stubbornly does not give this metal to man. Nowadays, a large number of gold mining, the most modern technology has been created, but the greatest effect in gold mining is provided by the ever-increasing knowledge of man about the properties of gold.