According to the different luster and color of gold, pure gold, k gold, real gold and fake gold can be roughly distinguished. In other words, red and yellow (yellow-red) is the best gold with a fineness of over 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".

Step 2 consider

With the same volume of silver, lead and tin, the weight of gold is about twice. Real gold feels like falling in your hand, while copper or others only feel heavy and don't fall.

3. Listen to the sound

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 older the person, the worse the color. Fake or low-quality gold sounds crisp and dull, generally making a "Dangdang" sound, with a lingering sound, and violently beating after landing.

4. Bending hardness

When high-quality gold is carved with pins or nails, it will 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.

5. Identify colors with touchstones.

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.

In the past, people often used a touchstone to determine the approximate content of gold. Touchstone is a mixed black carbonaceous mineral such as timely and opal. Draw a stripe on the touchstone to see the approximate fineness of gold. Pure gold: shiny deep yellow and thick yellow; Silver-bearing gold: light to red and green; Gold containing more than 25% silver: earthy white; Copper-bearing gold: the color is deepened, showing a red tone; Gold containing silver and copper: yellow; Gold containing zinc, copper and nickel: platinum.

Step 6 use acid spots

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.

Step 7 burn with fire

Burn the jewelry to be identified (don't make it melt and deform), and observe the color change after cooling. If the surface is still golden, it is pure gold; If the color darkens or turns black to varying degrees, it is not pure gold. Generally, the lower the fineness, the thicker the color, and all of them turn black, indicating that they are fake gold ornaments. When it really burns red, it is quenched into water and its color remains unchanged. It really doesn't change color in case of fire, it doesn't resist fire, and it becomes dark purple.

In an experiment, two kinds of gold with different purity, one containing a small amount of impurities and the other all gold, were melted by professional welding guns, and the melted gold showed completely different States. The gold necklace with low purity is dark in color and rough in section, and the place with flux is obviously black; But tiger balm is still as bright as new, and the melted surface is smooth and clean, even brighter than before.