1. 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, gold is preferably reddish-yellow (yellow-red), with a fineness above 95; true yellow, around 80; bluish-yellow, around 70; yellow with a hint of gray around 50. Therefore, the formula is "seven green, eight yellow, nine five red, yellow and white with gray and half gold". For jewelry that has been stored for a long time, there is a saying that "copper turns green, silver turns black, and gold never changes color."

2. Weigh the weight

Gold is about twice as heavy as silver, lead, and tin of the same volume. Real gold has a falling feel when held in the hand, while copper or other items only feel heavy but not falling.

3. Listen to the sound

When high-quality gold jewelry is struck or thrown on a hard ground, it will make a dull and low sound of "thud, thud", which is soundless and rhymeless. There is no elasticity. K gold has rhythm, sound and elasticity. The greater the elasticity, the sharper and longer the rhythm, the worse the quality. Fake or low-quality gold has a crisp sound without dullness. It usually makes a "dang-dang" sound with lingering sound, and beats violently after landing.

4. Hardness

High-quality gold can leave traces when scratched with a pin or fingernail. Gold jewelry with a fineness of 97 or above will have wrinkles at the bends after being bent two or three times, also called fish scales; gold jewelry with a fineness of around 95 will feel hard when bent, and the fish scales will not be obvious; gold jewelry with a fineness of around 90 will appear when bent. It is very hard when folded and has no fish scale pattern; gold jewelry containing a lot of impurities will break after being bent two or three times; if it is made of raw gold, it will break when bent, and the cross section will have an obvious sandy texture. When using this method, the width and thickness of the jewelry should be taken into consideration. Thick and wide jewelry will be harder, while thin and narrow jewelry will be softer.

5. Use a touchstone to identify the quality

Use a gold pair (a gold medal with a determined quality) and the jewelry being tested to grind on the touchstone, and determine the quality of the gold jewelry by comparing the colors. This method should be carried out under natural light and fluorescent lamps, not under direct sunlight and incandescent lamps.

In the past, people often used touchstones to determine the approximate content of gold. Touchstones are a mixed black mineral containing carbonaceous quartz and opal. If you draw a stripe of gold on the touchstone, you can see the approximate content of gold. Fineness. Pure gold: shiny deep yellow, rich yellow; silver-containing gold: light to slightly inflammatory green; gold containing more than 25 silver: earthy white; copper-containing gold: darker color, red tone; silver-containing copper Gold: yellow; gold containing zinc, zinc, and nickel: platinum.

6. Use acid points

Grind out the gold traces of the jewelry to be identified and the matching cards on the touchstone, and use a glass rod to spot nitric acid on the gold traces. Due to the chemical properties of the gold element It is stable and does not react with acid, so the color does not change. If it is not gold or pure gold, the golden path will disappear or change. The law of change is "three fast and three slow", that is, the low-quality gold disappears quickly, and the high-color gold disappears slowly; mixed gold disappears quickly, and clear gold disappears slowly; large mixed gold disappears quickly, and small mixed gold disappears slowly. Depending on the disappearance of the gold channel, the quality of the gold jewelry can be determined by comparing the cards.

7. Burn with fire

Use fire to burn the jewelry to be identified (do not melt or deform the jewelry). After cooling, observe the color change. If the surface still has the original gold color, it is pure. Gold; if the color darkens or becomes black to varying degrees, it is not pure gold. Generally, the lower the fineness, the thicker the color, and if everything turns black, it means it is fake gold jewelry. After it is really red-hot, it is quenched into water and the color remains unchanged. The real ones don't change color when exposed to fire, while the fake ones are not fire-resistant and turn black and purple, not shiny.

As an experiment, two pieces of gold with different purity, one containing a small amount of impurities and the other pure gold, were melted with a professional welding gun respectively. The melted gold showed completely different states. A gold necklace with low purity becomes darker in color, has a rough cross-section, and the areas where the solder is present are obviously black; while pure gold still shows the true color of gold as bright as new, and the melted surface is smooth and clean, even brighter than before.