Specifically:
Regular gold shops don't sell fake gold. According to national standards, precious metal jewelry must have relevant words. In the national standard, the purity and material mark of precious metals are expressed. For gold jewelry, it should be expressed by one thousandth of a fraction, or by k number, and used together with gold, Au or G. For example, pure gold can be expressed as AU990 or directly called pure gold. 18K gold can represent gold 750, AU750, G750, Au 18K, G 18K and so on. The most direct way is to observe the lettering on gold jewelry.
The most direct and effective way to judge the purity of gold is to test gold with fire. However, this method of identifying the purity of gold is harmful and will only be used when gold is recycled. There is a saying that "real gold is not afraid of fire", mainly because when the purity of gold reaches a certain level, the color of gold will not change when it is burned. However, 18K gold will appear black when it is still burned. Therefore, it is not recommended.
How to distinguish between true and false gold;
1. Identification
Jewelry imprint should contain manufacturer's code, name and content of precious metal materials.
2. Appearance quality
It is mainly the quality inspection of specific processes such as the overall modeling and processing quality of jewelry.
3. Jewelry weight
The price of gold jewelry is calculated according to the weight and processing fee, and the weight of jewelry is one of the important indicators. According to the standard, the weight of jewelry is measured in grams, and the tolerance of a single piece of gold jewelry is 0.01g.
4. Gold content of currency
The gold content of jewelry is an important indicator of its quality. There are many methods to test gold content, which can be divided into chemical analysis and instrumental analysis. According to whether jewelry is damaged in the process of testing, it can be divided into nondestructive testing and destructive testing. In the daily inspection of jewelry quality supervision department, nondestructive testing is the main method, and density method is combined with X-ray fluorescence spectrum, electron probe and other large instruments for analysis. Damage detection is the main method of market supervision and spot check, and fire assay is the national detection method for determining the gold content of jewelry in China at present.
Look at the color
According to the different luster and color of gold, pure gold, k gold, real gold and fake gold can be roughly distinguished. That is, red and yellow are the best gold, and the purity is above 95%; The fineness of positive yellow is about 80%; Cyan accounts for about 70%; Yellow is light gray, and the fineness is about 50%. Therefore, there is a formula of "seven green, eight yellow, nine five red, yellow and white with gray and half gold". For jewelry that has been hidden for a long time, there is a saying that "copper turns green, silver turns black, and gold never changes color".
6. Look at density
The density of gold is 19.32g/cm3, which is about twice as heavy as that of silver, lead and tin with the same volume. Available formula: the mass (gram) of a certain gold jewelry is equal to the density compared with the volume (cubic centimeter) of a certain gold jewelry. Calculate the density of the measured gold jewelry. If the density is about 19.32g/cm3, it is pure gold or relatively pure gold, otherwise it is impure gold or colored gold (this method is not destructive to jewelry).
7. Bending hardness
Gold has the characteristics of ductility and low hardness, and can be pressed into thin sheets with a thickness of 12.7 microns. When the color is dark, you can scratch it with a pin or nail to leave traces. More than 97% of colored gold jewelry is folded two or three times, and wrinkles appear at the bend, also known as fish scales; Gold ornaments with a fineness of about 95% feel hard when bending, and the scales are not obvious; About 90% of gold ornaments are hard when bending, and there are no fish scales; Gold jewelry with many impurities will break after two or three bends; If it is made of gold, it will break when bent, and there are obvious sand grains on the cross section. When using this method, the width and thickness of jewelry should be considered. Thick and wide jewelry is harder, while thin and narrow jewelry is softer.
8. Listen to the rhyme and see the elasticity
When high-quality gold jewelry is knocked or thrown to the hard ground, it will make a dull and low sound of "poof-poof-poof", which has no rhythm and elasticity. K gold has rhyme, sound and elasticity. The greater the elasticity, the sharper the rhyme and the worse the quality.
Verb (abbreviation for verb) uses touchstone to identify colors.
The color of gold jewelry is determined by grinding the gold card (the gold medal whose color has been determined) and the measured jewelry on the touchstone and comparing the colors. The method should be carried out under natural light and fluorescent lamps, not under direct sunlight and incandescent lamps.
10. Use acid.
On the touchstone, grind the gold channel of the identified jewelry and the correct brand respectively, and test nitric acid on the gold channel with a glass rod. Because the chemical property of gold element is stable and does not react with acid, its color remains unchanged. If it is not gold or impure gold, the path of gold disappears or changes. The law of change is "three fast and three slow", that is, the low color disappears quickly and the high color disappears slowly; Mixed gold disappears quickly, while clear gold disappears slowly; Large mixed gold disappears quickly, while small mixed gold disappears slowly. According to the disappearance of the golden path, the color of gold ornaments can be determined by comparing cards.