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First, there is no shortage of gold. Natural gold is still not absolutely pure, what's more, gold is rare and expensive. So many gold ornaments add some copper and silver to gold to make alloys. When people buy gold, they are faced with the problem of how to identify the uniform purity of gold and determine its color (gold content). With the golden eye of the touchstone, we can not only distinguish the authenticity of gold; You can also see through the pros and cons of gold (the unit is 24k …100%; 18k … 75% is the second; 12K...50% is bad) This is because the colors of gold ornaments with different colors are slightly different. People extract standard gold bars with different gold contents in proportion in advance, draw color marks with known contents one by one on the touchstone, then cut the gold ornaments to be tested on the same touchstone, compare the two, and finally judge the color by experienced experts. This method is simple and feasible, but there are some errors. We must find a more accurate method and choose a sharper instrument. With the development of science and technology, laser gold detector was invented abroad. The laser beam irradiates gold, alloy or imitation gold, and turns them into vapor respectively, showing different spectral lines and their intensities, so that it can be correctly identified, and the operation is simple without worrying about the loss of gold. During inspection, the knife made by laser is smaller than the needle tip, and the sample loss is less than one billionth of a gram. It is really very small and is very popular with customers and jewelers. This kind of apparatus for hanging all kinds of gold ornaments on Lushan Mountain is a veritable touchstone. ...

Second, how to identify jewelry,

Especially the authenticity of gold? China folks have summed up a set of simple methods, the formula of which is: look at Guanghua, weigh the weight, listen to the rhyme, fold the hardness, grind on the stone, compare the cards, use acid dots and fix the color. The first four sentences rely on perception and feeling; The last four sentences need tools and reagents. There are many kinds of jewelry that are easily confused with gold jewelry, such as gold-plated jewelry, gold-plated jewelry, copper jewelry and copper alloy jewelry.

1, look at the color:

Gold-plated jewelry is a layer of gold plated on the surface of other metal jewelry by electroplating. The color is similar to that of real gold jewelry, golden and bright, and it is not easy to identify when it is new. However, gold-plated jewelry is light, hard and toothless, and it is easy to fade when used for a long time. Some gold-plated jewelry with poor electroplating is either red or white or flowery.

Gold-plated jewelry is made by wrapping 24K or 22K gold foil on other metal surfaces. If the k value of gold foil is too low, its softness is poor. The appearance of gold-plated jewelry is similar to that of real gold jewelry, which is glittering, difficult to fade and difficult to distinguish between true and false. However, a careful observation of the dents, included angles, backs, etc. of jewelry will reveal that the gold foil is uneven and peeling. In addition, gold-plated jewelry is lighter in hand, harder in texture than pure gold jewelry, toothless, not easy to bend, and gold foil is easy to peel off when worn for a long time.

The color of copper jewelry is yellow with red, false, dull, soft and light. Copper alloy jewelry (copper-tin alloy) is white in color and hard and light in quality. Wearing it for a long time will fade and the skin will turn black.

The higher the purity of gold jewelry, the darker 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".

2. Look at the seal:

Whether it is gold-plated jewelry, gold-plated jewelry, copper jewelry or sub-gold jewelry, there is generally no seal similar to gold jewelry. Or stamps are different from gold jewelry, for example, some jewelry is engraved with the English letter "GK", which means "gilded". Or the seal is illegible and crooked. Consumers should judge the authenticity of gold jewelry by identifying whether there is a seal on the jewelry, whether the seal conforms to the above delineation, and whether the seal is clear.

Domestic gold ornaments are purified and prepared according to international standards, and stamped, for example, "24K" means "full red" or "pure gold"; 18K gold, marked with "18K". If the fineness is lower than 10K, the K-gold seal number cannot be printed as required.

3, look at the 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 raw gold, it will break when bent, and there are obvious sand grains on the cross section.

4. Look at the 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. If the formula is used, it is: the mass (gram) of a gold ornament is higher than the volume (cubic centimeter) of a gold ornament, which is the density. 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).

5. Listen to the sound:

Real gold with a purity of more than 99% will beep when thrown on the hard ground, which is disorganized and elastic. Fake or low-quality gold sounds crisp and dull, generally making a "Dangdang" sound, with a lingering sound, and violently beating after landing.

6, with acid point:

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 properties of gold are not chaotic and do not react with acids, the 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.