Because gold is not easy to mine, mining cost is high, good physical characteristics, so in the long-term development of social history, gold is not only used as a decorative, but also be given the monetary value of the function. Until the 1970s, gold from the direct monetary role in the separation, that is, gold demonetization. But as a precious metal, gold is still the world's main international reserves. According to the gold reserves announced in 2000, the world's gold reserves in the top 10 countries and international institutions are: the United States (8137 tons), Germany (3469 tons), the International Monetary Fund (3217 tons), France (3025 tons), Switzerland and the earth (2494 tons), Italy (2452 tons), the Netherlands (912 tons), Japan (764 tons), the European Bank (747 tons) and Poland (60 tons). 747 tons) and Poland (607 tons), with the United Kingdom and China in 11th place (538 tons) and 14th place (395 tons).
There are two main ways to categorize gold: one is by nature, the other is by form. Classification by nature is based on the internal color of gold products and characteristics of different classifications. According to the form of classification is based on the external shape of the classification of gold products. According to the nature of points, gold can be divided into "raw gold" and "cooked gold" two categories. Raw gold is also called "original gold", "natural gold" or "barren gold", is the people from the mine or riverbed mined, unrefined gold. Mined from the riverbed is generally sandy, also known as "sand gold". Mined from the gold mine is called "vein gold", also known as "rock gold". Where the gold after refining is called "cooked gold", is often said to be pure gold, red gold and color gold, etc. General term. Cooked gold due to the addition of other elements and make gold in the color changes, people usually be added to the metal silver and no other metal cooked gold for the 'clear color gold', and was mixed into the silver and other metals of gold to become a 'mixed color gold'. k gold is a mixed color gold color K gold is mixed color gold color a way of expression, 4.1666% gold composition for 1K. gold according to K gold color high and low can be expressed as 24K, 22K, 20K and 18K, etc. 24K gold gold content of 99.998%, basically regarded as pure gold, 22K gold content of 91.665%. Gold color can also be directly with the percentage of content, usually the weight of gold into 1,000 parts of the expression, such as gold pieces labeled 9999 for 99.99%, and labeled 586 for 58.6%. Gold according to the form of points is more diverse, such as blocks, bars, coins, ingots, leaves, silk and powder, etc., the folk also said "melon gold", "weight gold" form of gold.
In the precious metals market or gold market there are two other precious metals. That is, platinum and silver. Platinum is a product made from platinum metal. The chemical symbol of platinum is Pt, has excellent corrosion resistance, oxidation resistance and beautiful color, so the band is used as raw materials for jewelry. China's current market common white gold jewelry there are 3 kinds, namely Pt990, also known as full white gold, platinum content of not less than 1,000 parts 990; Pt900, platinum content of not less than 1,000 parts 900; Pt850, platinum content of not less than 1,000 parts 850. silver in the air for a long time will be reacted with sulfide in the air, the color is easy to turn black, its chemical symbol for Ag, the market silver products color Generally identified as S990, silver content of not less than 990 parts per thousand; s925, silver content of not less than 925 parts per thousand; S800, silver content of not less than 800 parts per thousand. gold products on the market color marking there are two kinds of: one is the percentage of, such as G999, etc.; the other is the K gold, such as G24K, G22K and G14K, etc..