Precious metal elements are scarce in the Earth’s crust, of which gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), ruthenium (Ru) these eight belong to precious metals.
The earliest metal mined and used by humans is called the “king of metal.” It is chemically stable and will not oxidize even if burned in the air until it melts. Pure gold is natural in mineralogy, has an isometric crystal system, golden yellow, metallic luster, Mohs hardness 2.5, excellent ductility, 1g gold can be stretched into 3420m filaments, density 19.32g/cm³.
The gold content of pure gold is not less than 990, and the imprint is “Au990” and “G990”. All solid gold sold on the market is marked with “Au999”.
K is an international unit, and the gold content is 24k when the thousand fraction is 1000. The gold content of 1K gold is about 41.66‰. Common k gold such as 22K (916‰), 18K (750‰), 14K (585‰), 9K (375‰). The marks are “Auxxx”, “Gxxx”, “GxxK”. Color gold also belongs to K gold, the color formed by melting other metallic elements into the gold matrix. The three primary colors of color k gold are yellow k gold, white k gold, and red k gold.
Silver was discovered and used in China 4,000 years ago and is the most widely used precious metal today. Silver occurs in nature primarily as elemental silver and is produced as a compound: metallic luster, silver white, Mohs hardness 2.7, and good conductivity. With good ductility, 1g silver can be stretched into 1800-2000m filaments. The chemical properties are relatively stable, with no oxidation at room temperature but poor corrosion resistance; in humid air with sulfur-containing substances or gases containing sulfur dioxide and hydrogen sulfide, it will react to produce black silver sulfide. Silver compounds are also sensitive and respond with arsenide and halogen elements to form black silver arsenide and halide. It does not react with dilute nitric acid and dilute hydrochloric acid. However, it can respond quickly with nitric acid to form silver nitrate.
Sterling silver: the silver content is not less than 999, marked “S999”.
925 silver: the silver content is not less than 925, marked “S925” or “Ag925”.
800 silver: the silver content is not less than 800, marking “S800” or “Ag800”.
The highest purity of silver and its silver alloy jewelry is 999; higher than 999‰ can only be called a thousand silver; Minimum 800, less than 800‰ can not be called silver jewelry.
The Miao nationality silver: Miao unique silver is an alloy of silver, white copper (copper-nickel alloy), and nickel. The silver content is usually 20% to 60%. The composition is mainly copper.
Tibetan silver: Traditionally, 30% silver, +70% copper, and white copper are mixed with a small amount of silver. There is a silver deposit that does not contain silver, which is white copper.
Thai silver: Also called black silver. Jewelry that has been specially aged using the properties of silver blackening with sulfur.
The platinum group consists of six elements:
The platinum group has a high melting point and is a refractory metal. Currently, only platinum and palladium in the platinum group can be used as jewelry.
Platinum is a heavy metal with high density and low hardness and has good electrical conductivity, thermal conductivity, and ductility.
Pure platinum: platinum content of not less than 999‰, imprint “pt999”
990 platinum: thousand fractions not less than 990‰, imprint “pt990.”
950 platinum: not less than 950‰, stamped “pt950”
900 platinum: not less than 900‰, stamped “pt900”
850 platinum: not less than 850‰, stamped “pt850”
Palladium is a newly developed jewelry precious metal in recent years, similar to platinum, and the price is relatively low.
Pure palladium: Palladium content of not less than 999‰, imprint “Pd999”
990 palladium: not less than 990‰, stamped “Pd990”
950 palladium: not less than 950‰, marked “Pd950.”
500 palladium: not less than 500‰, stamped “Pd500.”
Color Palladium: Palladium and enamel are made by a unique process.
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