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Gold, the symbol of the chemical element Au, is a soft, golden yellow and corrosion-resistant precious metal. Gold is valuable, and its value content is relatively high. The international gold price unit is USD/oz, while the China gold price unit is RMB/gram. If you want to participate in future gold investment and get the opportunity of increasing investment value in the gold market, you must understand the attributes, characteristics and functions of gold in monetary finance. Gold is one of the rarest and most precious metals in the metal kingdom. In ancient times, it was mainly used as currency, decoration and jewelry, and it was the most precious metal. At 175 1, platinum was found, which is more scarce, more widely used and more difficult to extract, so it is more precious. So now, gold has changed from the first precious metal to the precious metal alongside platinum, but it is still the most popular precious metal as jewelry material and electronic information material because of its pure texture, bright color and many excellent characteristics.

[Edit this paragraph] 1. Physical and chemical characteristics of gold

Physical and chemical properties of 1. 1

Gold (transition metal)

Crystal structure: face-centered cubic structure

Atomic weight: 196.5504

Shell structure: 2,8, 18,32, 1 8,1.

Electronic configuration: [xe] 4f145d106s1.

Valence: 1, 3

Melting point: 1064.43℃

Boiling point: 2808℃

Electronegativity: 2.54

* * * Price radius:1.34a.

Ion radius: 0.85 (+3) a.

Atomic radius:1.79a.

Atomic volume:10.2cm3/mol

First ionization potential: 9.2257V

Secondary ionization potential: 20.521v.

Oxidation state: (3), 1

Density at 293K:19.32g/cm3.

Specific heat capacity: 0. 128J/gK

Heat of vaporization: 334.4kJ/mol

Heat of fusion: 12.55kJ/mol.

Electrical conductivity: 0.452x10 6/cm ω/cm ω.

Thermal conductivity: 3. 17W/cmK

Elastic coefficient: 78.3 X 10E3 MPa.

Coefficient of thermal expansion:14.2x10 (-6)/k.

Lattice parameter: 4.0786A

Mohs hardness: 2.5

1.2 physical properties

Color: The beauty of golden yellow is comparable to that of the sun. The steam released when gold melts is green; Its gold powder is usually brown when it is melted; If it is cast into thin slices, it can transmit green light.

Ductility: unusually strong. 1 oz gold can be stretched to 50 miles long, and its ductility makes it easy to cast, making it a good choice for making jewelry. Of all metals, gold has the greatest pulling force.

Extensibility: second to none. It will cause extremely thin gold sheets to roll up easily. Gold weighing 1 ounce can be hammered into 1 foot thickness and 100 square foot thickness. The ancients hammered it into thin slices and threw it into temples and palaces for decoration. It is said that 1 ounce of gold can be used to build the roof of a house. If you have a chance to visit these ancient temples, you should pay attention, otherwise free gold coins will fall on your head!

The color of gold is golden yellow, with metallic texture and no cleavage. Hardness 2-3, pure gold 19.3, melting point1070℃; Good ductility, can be pressed into thin foil, and has high heat and thermal conductivity. Pure gold is the best electronic conductor material.

As a precious metal, gold has good physical properties. "Real gold is not afraid of fire" means that gold is not easy to melt under the general flame. High density and heavy touch. Good toughness and ductility, good electrical conductivity. Pure gold is bright yellow, but the color changes greatly after mixing with other metals, such as gold-copper alloy is dark red, and silver-containing alloy is light yellow or grayish white. Gold is easily ground into powder, which is also the reason why gold is dispersed in nature. Pure gold jewelry is also easy to wear and lose weight.

In Mendeleev's periodic table, the atomic number of gold is 79, that is, there are 79 negatively charged rotating electrons around the nucleus of gold, so gold has good chemical stability. In the metal market, metals such as gold, ruthenium, rhodium, palladium, osmium, iridium and platinum are collectively called precious metals.

Gold is a very soft metal, but it is not as good as lead and tin. It can trace on pure gold with nails, which makes gold very easy to process. But this is not ideal for the manufacturers of decorations, because it is easy to scratch the decorations, make them lose their luster and even affect their appearance. Therefore, when gold is used to make jewelry, copper and silver are usually added to improve its hardness.

Gold is easy to forge and extend, and can be ground into transparent and green gold foil with a thickness of 0.001mm. 0.5g of gold can be drawn into160m long gold wire.

Gold is easy to wear and become very fine powder, so gold is often widely distributed in nature in a dispersed state.

Gold is a good conductor of heat and electricity, but it is not as good as platinum, mercury, lead and silver.

The melting point of gold is 1063. C, molten gold has high volatility, and its volatility increases with the increase of temperature.

The compressive strength of pure gold is 10 kg/mm2, and the tensile strength is related to the pretreatment method, generally between 10-30kg/ mm2. When the gold wire is cold-drawn, the force is the greatest.

Pure gold has excellent grass yellow metallic luster. It can be said that gold is the yellowest of all metals. There is no pure gold in nature, and metallic impurities (first of all, copper and silver) give gold various colors and tones, from light yellow to bright yellow and red. The color of gold also depends on the thickness of the metal block and its aggregation state. For example, thin gold foil is green under the light, so is molten gold, while unmelted gold is yellow-green, and finely dispersed gold is generally deep red or deep purple.

Natural gold is sometimes covered with a thin film of iron oxide. In this case, the color of gold may be brown, dark brown or even black.

Gold can alloy with many metals, because the atomic radius of these metals is very close to that of gold. The atomic radius of gold is equal to 1.46 angstrom; Bismuth 1.46 angstrom; Silver 1.44 angstrom; Platinum 1.39 angstrom. Therefore, gold can form gold-silver alloy, gold-copper alloy, gold-platinum alloy, gold-palladium alloy and so on. These alloys are not compounds, but solid melts. All metals in the alloy have lower melting points than pure metals. If gold is heated to near the melting point, it can be melted like iron, and fine gold particles can be melted into gold nuggets. (1 angstrom = = 0.00000000 l cm)

Gold powder must be pressurized to fuse together at low temperature.

Melting gold with other metals can not only reduce its melting point, but also change the mechanical properties of gold itself. Containing silver and copper can obviously improve the hardness of gold; Containing arsenic, lead, platinum, silver, bismuth and tellurium can make gold brittle, and lead is more prominent in this respect. If the alloy containing only 1% lead is stamped, it will become fragments. If pure gold contains 0.0 1% lead, its good ductility will be completely lost.

Gold has the ability to absorb x-rays.

Gold is included in the list of compounds, just like the precious metal family, but it can react with some elements after all. Especially with halogen (chlorine, bromine, iodine) compounds to generate AuCl or AuC 13. Gold can also be combined with cyanide, mercury and hoof. In fact, there are only compounds of gold and hoof in nature, and there are few compounds of gold and mercury. All other compounds are manufactured by hand, and "regin" (Au (NH) 3 (CH) 3) can also be manufactured by hand. "Regin" is easy to explode when it is impacted or heated.

Although gold is difficult to dissolve, it can still be dissolved in some solutions. A small amount of gold can also be dissolved in water containing chlorine, sulfuric acid or corrosive acid. In aqua regia and dilute cyanide solution, it is dissolved in a large amount in ionic state.

The crystal of gold belongs to the equiaxed system. Crystals are usually cubic or octahedral in shape. The crystal melts and then condenses, which is an irregular polygon. The slower the cooling, the bigger the crystal.

1.3 chemical properties

Gold has stable chemical properties and strong corrosion resistance. Generally, it is not oxidized from normal temperature to high temperature in air, and it is insoluble in single strong acid gold such as hydrochloric acid, nitric acid and sulfuric acid, but only soluble in mixed acid (aqua regia) of hydrochloric acid and nitric acid to generate chloroauric acid H [AUCL 4]. At room temperature, in the presence of oxygen, gold can be dissolved in a solution containing potassium cyanide or sodium cyanide to form a stable complex M [Au (CN) 2]. Gold can also be dissolved in a solution containing thiourea; It is also dissolved in an acidic solution containing chlorine. Gold does not react with alkali solution, but it can react with sodium peroxide in molten state to generate NaAuO2 _ 2. The valence of gold is-1, -2,+1, +2, +3, +5, +7 and so on. The oxide is gold trioxide and the chloride is gold trichloride. In acidic medium, chloroauric acid H [AUCL _ 4] or complex M [Au (CN) _ 2] can be reduced to elemental gold powder by metal zinc (zinc powder or zinc wire), sodium sulfite and hydrazine hydrate. The sulfide of alkali metal will corrode gold and produce soluble sulfide gold. Humic acid in soil and metabolites of some bacteria can also dissolve trace amounts of gold.

The ionization potential of gold is very high, so it is difficult to lose the outer electrons and turn them into positive ions, and it is also difficult to accept that electrons turn into anions. Its chemical properties are stable and its affinity with other elements is weak. So it exists in the form of simple substance in nature, that is, natural gold.

The average content of gold in the crust is about 65438+1.1(0.001ppm), and the average content of gold in seawater is about 65438+1(0.00001ppm). The grade of gold in gold mines with general industrial value is 2-3g/ton, that of rich ore is 5-50g/ton, and that of ultra-rich ore is 50-500g/ton. There are gold nuggets, ranging from the smallest10g to the largest dozens of kilograms and hundreds of kilograms of rare gold nuggets. Because some of them are shaped like dog heads, they are commonly known as gold nuggets. Indian scientists have discovered two gold nuggets weighing nearly 2.5 tons. The lean ore is 0. 1- 1 g/ton, which has an industrial mining value of more than 0.5 g/ton at the current level of metallurgical technology.

Pure gold is rare in nature, and often contains associated elements such as silver, copper, iron, palladium, bismuth, platinum, nickel, tellurium, selenium and osmium. Those natural gold with silver 15% or more are called silver-gold mines, those with copper over 20% are called copper-gold mines, and those with palladium 5- 1 1%.

Gold likes sulfur, and often closely coexists with sulfides such as pyrite, arsenopyrite, galena and stibnite. It is easy to form intermetallic compounds with sulfur-loving silver, copper and other elements.

Jin xitie The content of gold in meteorites (1150x10-12) is three orders of magnitude higher than that in ordinary rocks, and gold often forms intermetallic compounds with iron-loving platinum group elements.

Gold also has chalcophile affinity, which occupies the edge position between copper-loving and iron-loving elements in the periodic table of elements, and belongs to the same subgroup as copper and silver. In the reducing geological environment, the geochemical behavior of gold is similar to that of adjacent elements, showing stronger iron affinity, and copper and silver are mostly enriched in sulfide phase. Gold and platinum are mostly concentrated in the metal phase. The elemental abundance of gold in the earth is 0.8× 10-6, the core is 2.6× 10-6, the mantle is 0.005× 10-6 and the crust is 0.004× 10-6. The abundance of gold in the crust is only1100000 for iron and 1/2 1 for silver.

More than 99% of the gold on the earth enters the core. This distribution of gold was formed during the long-term evolution of the earth. The crust formed in the early stage of the earth's development is rich in gold, so it can generally represent the Archean greenstone belt composed of early residual crust, especially the combination of mafic and ultramafic volcanic rocks. The abundance value of gold is higher than that of various rocks in the crust, which may become the earliest "source bed" of gold deposits.

To sum up, the abundance value of gold in the crust is very low, and it has the properties of sulfur-loving, sulfur-loving, iron-loving and high melting point. In order to form industrial deposits, gold should be enriched thousands of times, and in order to form large and rich mines, gold should be enriched thousands of times, tens of thousands of times or even higher. It can be seen that its huge gold deposits generally go through a long geological period, which may be formed by multi-source and multiple mineralization.

The main uses and functions of gold,

1. Used as international reserve.

2. Value preservation function

3. Hedging function

4. Used as jewelry decoration

5. Application of industrial technology

[Edit this paragraph] 2. Types of gold deposits

Gold is a natural product that exists in a free state in nature and cannot be synthesized artificially. According to the different sources and refined contents, it can be divided into raw gold and cooked gold.

Raw gold, also known as natural gold, barren gold and raw gold, is a semi-finished product of mature gold, which is mined from mines or alluvial deposits at the bottom of rivers without melting and refining. Raw gold can be divided into ore gold and placer gold.

2. 1 ore gold

Also known as synthetic gold, it occurs in mines and gold mines. Most of them are deposited together with underground hot springs through rock crevices, and there is often time in the rock crevices. Mineral gold is mostly associated with other metals, including silver, platinum, zinc and other metals, which were called alloy gold before other metals were put forward. Mineral gold is produced in different mines and contains different other metals, so the fineness varies, generally between 50% and 90%.

2.2 placer gold

Placer gold deposit is the main gold deposit in the world, but after thousands of years of mining, most of the ore-rich sand has been exhausted, and now it is mainly ore gold. Placer gold is gold produced at the bottom of river bed and bend or in low-lying areas, mixed with stone and sand and washed out. The placer gold mine originated from the mine. As the gold ore was exposed to the ground, after a long period of wind and rain, the rock weathered and cracked, and the gold broke away from the vein and went down with the sediment, naturally settling in the sand, and deposited as a gold-bearing layer on the river bottom or under the sand, thus forming the placer gold mine. The characteristics of placer gold are: the particle size is different, the big one is like broad bean, the small one is like fine sand, and the shape is different. The color varies with the fineness. More than 90% is red and yellow, eight is light yellow and seven is cyan yellow.

[Edit this paragraph] 3. Global distribution of gold mineral resources

At present, the proven gold resources in the world are 89,000 tons, with a reserve base of 77,000 tons and a reserve of 48,000 tons. More than 80 countries in the world produce gold. South Africa accounts for 50% of the world's proven gold resources and reserves, accounting for 38% of the world's reserves; The United States accounts for 12% of the world's proven resources, 8% of the world's reserve base, and 12% of the world's reserves. In addition to South Africa and the United States, the main gold resources are Russia, Uzbekistan, Australia, Canada and Brazil. Among more than 80 gold producers in the world, America accounts for 33% of the global output (including Latin America 12%, Canada 7% and the United States14%); Africa accounts for 28% (including South Africa 22%); 29% in Asia-Pacific region (including Australian 13% and China 7%). Countries with annual output exceeding100t include Indonesia and Russia in addition to the above five countries. Countries with an annual output of 50-100t include Peru, Uzbekistan, Ghana, Brazil and Papua New Guinea. In addition, Mexico, Philippines, Zimbabwe, Mali, Kyrgyzstan, South Korea, Argentina, Bolivia, Guyana, Guinea and Kazakhstan are also important gold producers.

[Edit this paragraph] 4. The texture of gold

Mature gold is the gold after smelting and purifying raw gold, which is generally high in purity and fine in density, and some of it can be directly used in industrial production. Common are gold bars, nuggets, ingots, various ornaments, utensils, gold coins, industrial gold wires, sheets and plates. Because of different uses, the required fineness is different, or because there is no purification equipment, only unpurified gold is melted, or the purity is not enough to form gold with different fineness. It is customary to divide mature gold into pure gold, red gold and colored gold according to its fineness. Gold with a fairly high purity after purification is called pure gold, and gold generally refers to pure gold with a purity of over 99.6%.

The meaning of red gold and pure gold is similar, but the standard of red gold varies with time and place. Gold with a purity of 99.6% sold in the international market is called red gold. Domestic red gold is generally between 99.2% and 99.6%.

Color gold, also known as "secondary gold" and "tidal gold", refers to gold with low fineness. Due to the different contents of other metals, the purity of these gold is as high as 99% and as low as 30%.

According to the classification of other metals, ripe gold can be divided into solid gold, mixed gold and K gold. Clear gold means that gold is only mixed with silver, regardless of its fineness. Clear gold is more common in gold bars, ingots, nuggets and various utensils and gold ornaments.

Mixed color gold means that besides silver, gold also contains other metals such as copper, zinc, lead and iron. According to the different types and quantities of metals, it can be divided into small mixed gold, large mixed gold, bronze mixed gold and lead mixed gold.

K gold refers to the gold prepared by silver and copper in a certain proportion according to the formula that pure gold is 24k. Generally speaking, the more silver in K gold, the bluer the color; If the proportion of copper is large, the color is purple. In the early days of liberation, China's K gold was calculated according to the standard of15% per K4. After 1982, it has been harmonized with international standards, taking1666% as the standard. When other elements are added to cooked gold, the color of gold will change. People usually refer to the ripe gold containing only silver and no other metals as "pure gold" and the gold containing silver and other metals as "mixed gold".

[Edit this paragraph] 5. golden

The purity of gold and its products is called success or fineness.

More than 200 years BC, the Greek mathematician Archimedes worried about judging whether a crown was made of pure gold. When he was taking a bath in the bathtub, he discovered what later generations called Archimedes' law of specific gravity: an object immersed in a liquid was subjected to upward buoyancy; Buoyancy is equal to the weight of the liquid it displaces. Thereby successfully confirming whether the crown made by the king is made of pure gold. So, how to express the purity of gold?

5. 1 Use "k gold" to indicate the purity of gold.

Theoretically, we call gold with a content of 100% 24K; ; Therefore, the calculation method is 100/24 (the national standard is in brackets): the national standard GB 1 1887-89 stipulates that the gold content per k (abbreviation of English carat and German carat, often written as "k") is 4. 16666%.

9k= 100/24*9=37.5% (375‰)

14k =100/24 *14 = 58.333% (585 ‰), which is set to 58.5% for easy identification.

18k = 100/24 * 18 = 75%(750‰)

22k =100/24 * 22 = 91.66666% (916 ‰) is set to 9 1.6% for easy identification.

In theory, 100% gold can be called 24K gold, but in reality it is impossible to have 100% gold, so China stipulates that gold with a content of more than 99.6% (including 99.6%) can be called 24K gold.

These kinds of K gold contents are general specifications of jewelry, and gold jewelry below 9K cannot be called gold jewelry.

5.2 Use words to express the purity of gold

Some gold ornaments are marked with words, which stipulate that the gold content is not less than 990‰, and the gold content of thousands of gold is more than 999‰.

In China, the imprint and identification card of gold products are stipulated. Generally, it is the manufacturer's code, material name, content stamp, etc. They are all necessary, and products without marks are unqualified. The same is true internationally. But for some very small products, it is also allowed to be unmarked.

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12. 1 The main needs and uses of gold can be divided into three categories.

1). Used as international reserve. This is determined by the monetary commodity property of gold. Because of its excellent characteristics, gold has played a role as a currency in history, such as a measure of value, a means of circulation, a means of storage, a means of payment and a world currency. Since the decoupling of gold and the dollar in 1970s, the gold function of money has also weakened, but it still maintains a certain monetary function. At present, gold still occupies a very important position in the international reserves of many countries, including major western countries.

2). Used as jewelry decoration. Gorgeous gold ornaments have always been a symbol of one's social status and wealth.

3). Application in industry and science and technology. Because of its unique and perfect characteristics, gold has extremely high corrosion resistance stability. Good electrical and thermal conductivity; The gold nucleus has a large effective cross section to capture neutrons; The reflection ability of infrared ray is close to100%; It has various catalytic properties in gold alloys; Gold also has good manufacturability and can be easily processed into ultra-thin gold foil, micron gold thread and gold powder; Gold is easy to be plated on the surface of other metals, pottery and glass, and it is easy to be welded and forged under certain pressure. Gold can be made into superconductors and organic gold. It is precisely because of its many beneficial properties that it has reason to be widely used in the most important modern high-tech industries, such as electronic technology, communication technology, aerospace technology, chemical technology, medical technology and so on.

12.2 gold market supply and demand

The supply sources of the gold market mainly include the following aspects: new gold produced by gold-producing countries in the world, gold sold to the world market by the former Soviet Union, gold recovered and reused, gold sold by official institutions of other countries, the International Monetary Fund and private individuals.

There are three main characteristics of gold supply in the gold market. The first is regular supply. This mainly includes the world, including the major gold producers in the world, and this supply is stable and regular. The second is to induce supply. This is due to the supply caused by other factors, mainly the rising price of gold, which makes many gold hoarders sell for profit or accelerate the mining of gold. The third is to supervise supply. This is an irregular supply in stages. If oil-producing countries are depressed by oil prices, they will sell some gold because of insufficient income.

The world's demand for gold mainly comes from official reserves, industrial and jewellery gold and investment demand.

(1) The official gold reserves of various countries are mainly used as international payment reserves, and the amount of a country's gold reserves is closely related to its foreign debt repayment ability. In order to maintain a certain proportion of gold reserves, central banks and international financial institutions will participate in trading activities in the world gold market.

(2) The increase or decrease of industrial demand has a great influence on the fluctuation of the world gold price. Gold has a wide range of industrial uses, mainly in jewelry, chemical industry, aerospace, electric power and other industries.

(3) Investment demand is also an important part of the source of demand in the gold market. On the one hand, people use the fluctuation of gold price to enter the market to earn profits. On the other hand, people can choose between gold and other investment tools under different conditions. If the dollar depreciates, the oil price rises and the demand for gold increases; If the stock market rises and attracts a lot of money, the demand for gold may decrease accordingly.

[Edit this paragraph] 14. How to invest in gold jewelry

Gold jewelry has a long history and is dazzling. After the 1980s, with the development of social economy, the improvement of people's living standards and the continuous improvement of people's cultural quality, gold ornaments have entered the daily life of ordinary people more and more widely.

1. Seal: According to the national product standards, jewelry products should have the color code of "Pure Gold 990" or "Thousand Gold 999" and the manufacturer's seal.

2. Color: Pure gold or thousands of gold is bright golden yellow, while the luster of copper is eye-catching.

3. Weight: The density of gold is more than twice that of copper. The same volume of gold and copper, gold has obvious drop feel.

4. Hardness: When you scratch on pure gold or thousands of pure gold with your nails, there are tiny marks, but you can't scratch on copper.

How to buy platinum series jewelry

1. Seal: According to the national product standard, platinum jewelry should have platinum chemical symbol Pt, platinum content and manufacturer's seal.

2. Color: Platinum jewelry is silvery white with gray tone, bright and never discolors, while silver is mostly yellow-white, while gold is not as bright as platinum, and white is bluish yellow.

3. Weight: The density of platinum is more than twice that of silver, and platinum, silver and platinum with the same volume have obvious falling feeling.

4. Hardness: Because platinum is harder than copper, it can't be scratched with copper wire, while silver is scratched with copper needle.

How to choose inlaid jewelry

1. Check whether the gems on the inlaid ornaments are loose.

2. It is best to have an appraisal certificate from a local testing institution.

3. Observe with the help of relevant detection tools, such as magnifying glass and diamond pen.

By trying on and comparing, you will have more buying experience.