Types of precious metals and their required content levels

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I. Types of precious metals and their purity requirements 1.1 Precious metals such as gold, silver, platinum, and palladium According to GB11887–2002 \"Specifications for the purity of precious metals in jewelry and methods of naming them\", precious metal jewelry available on the market can be divided into four categories: gold jewelry, silver jewelry, platinum jewelry, and palladium jewelry. 1.1.1 Gold jewelry can generally be classified into 18K gold, pure gold, and 24K gold, depending on the gold content. 1K is equal to 100% divided by 24, which means 1K is approximately 4.1667%. The theoretical purity of 24K is 100%. ①Jewelry made of 18K gold has a gold content of not less than 750‰, and can be labeled as 18K or G18K, G750, Au750, 18K gold, or 750 gold. ②Pure gold jewelry has a gold content of not less than 990‰, and can be labeled as pure gold or G990, Au990, or Gold 990. ③Jewelry made of 24-karat gold has a gold content of not less than 999‰, and can be labeled as 24-karat gold or G999, Au999, or Gold 999. In addition, gold jewelry such as 9K (with a gold content of not less than 375‰), 14K (with a gold content of not less than 585‰), and 22K (with a gold content of not less than 916‰) is also available on the market (especially abroad). 1.1.2 Silver jewelry: Common silver jewelry available on the market includes ①925 silver; the remaining 75‰ may be copper or antioxidant elements, and it can be labeled as S925 or Ag925, or silver 925. ②Pure silver requires a silver content of not less than 990‰, and can be labeled as S990 or Ag990, or Silver 990. Occasionally, 800 silver can also be seen (with a silver content of no less than 800‰). In recent years, it has been found that manufacturers, in order to prevent silver jewelry from oxidizing, often coat the surface of 925 silver and pure silver with a layer of nickel. If not checked carefully, this can easily lead to the mistake of considering such items as fake or imitation silver products. 1.1.3 Platinum jewelry Platinum is also known as white gold. In recent years, as consumer standards have continued to rise, platinum jewelry has become increasingly popular among male and female consumers in both urban and rural areas. In the jewelry market, common platinum jewelry includes Pt900, Pt950, and Pt990. ①Pt900: requires that the platinum content be no less than 900‰, and can be labeled as Pt900 or Platinum 900. ②Pt950: requires that the platinum content be no less than 950‰, and can be labeled as Pt950 or Platinum 950. ③Pt990 requires that the platinum content be no less than 990‰, and can be labeled as Pt990 or Platinum 990, or Pure Platinum. Occasionally, Pt850 (with a platinum content of not less than 850‰) and Pt750 (with a platinum content of not less than 750‰) can also be seen. 1.1.4 Platinum jewelry: This precious metal has only begun to be used specifically in the production of jewelry this year; previously it was used as an additive in platinum jewelry. It represents another new member in the family of precious metal jewelry. The commonly available palladium jewelry on the market mainly includes Pd950 and Pd990. ①Pd950 requires that the palladium content be no less than 950‰, and can be labeled as Pd950 or Palladium 950. ②Pd990 requires that the palladium content be no less than 990‰, and can be labeled as Pd990 or Palladium 990. Palladium jewelry with palladium contents of not less than 750‰ and 500‰ is mainly used for inlaying. Palladium jewelry shall not be referred to with ambiguous names such as “palladium-platinum jewelry” or “palladium-iridium jewelry”. In addition, the standards require that the weight of precious metal jewelry be expressed to two decimal places; for pieces with a weight of 100 grams or less, the negative deviation in weight shall not exceed 0.01 grams. 1.2 Other imitation jewelry: There are also a small number of the following accessories that were or are still available on the market: ① Gold-plated items: These involve shaping gold into extremely thin sheets of gold foil, which are then applied to materials based on copper, silver, zinc, nickel, etc., to create various jewelry pieces. This method is inexpensive yet gives the appearance of real gold. Jewelry is often marked with 24KF or 18KF. ②Gold plating: This process utilizes the principle of electrolysis to apply a layer of gold onto the surface of a metal substrate; the thickness of this layer is usually 10 microns or more. The metal substrates are often copper, silver, zinc, nickel, or their alloys. It is characterized by an extremely thin gold layer, easy plating, low cost, and a certain decorative effect; however, the gold layer tends to wear off, resulting in jewelry that only retains its brilliance for a short period of time. Jewelry often bears the marks 18KGP and 24KGP. ③Yajin: A gold-like material based on copper, which is often plated with gold on its surface. ④Noble metal: It actually does not contain gold; it is a yellow alloy that appeared in recent years, mainly composed of copper, nickel, and other elements, with small amounts of rare earth elements included. ⑤Titanium gold: It is rare in the market and is also a type of gold-like jewelry; titanium is plated on the surface of the base material to form a substance called TiN. In addition, jewelry known as Taiwan gold, Thai gold, and forged gold has also appeared on the market. These are all imitation gold jewelry; they are not genuine gold accessories made in those regions, but rather things that are plated with gold or covered with gold plating. Even in some tourist area markets, there are jewelry items labeled as “gem gold,” which are actually also gilt or plated products. 2. The difference between “platinum” and the so-called “K-platinum”: Platinum is another name or common term for platinum (Pt), and it is a precious metal that is more valuable than gold. With a density of 21.43 g/cm3 and a melting point of 1773°C, these values are higher than those of gold; however, their production volume is only 1/20 that of gold. It is a precious metal with better chemical stability, and it is rarer, more valuable, and holds its value better than gold. Platinum jewelry has been very popular in recent years, with platinum-set jewelry being particularly favored by people. ““K Platinum” is not K platinum; it is a white version of K gold (its English name is White Gold), while platinum’s English name is Platinum. The so-called 18K white platinum jewelry available on the market is actually white 18K gold jewelry; it ensures that the gold content is not less than 750‰, with the remainder being copper, zinc, nickel, silver, palladium, rhodium, and other elements. Due to different composition ratios, various colors can also be produced, resulting in 18K colored gold jewelry. To prevent misleading consumers, the standards stipulate that the terms “K platinum” or “white K gold” shall not be used; instead, it must be labeled as “white 18K gold” or simply “18K gold”. 3. The reason for the lower content in the stem of earrings and at the joints of bracelets or necklaces (or hinges) is that pure gold and pure platinum are relatively soft and lack strength. The stem of earrings as well as the joints of bracelets or necklaces (or hinges) require a certain level of strength, so pure gold or pure platinum is not suitable for use in these areas; instead, gold or platinum with a purity of around 900‰ or lower is generally used (standard GB11887–2002 stipulates that the purity of these areas must be no less than 750‰)