1. Gemstone jewelry, such as diamonds, rubies, sapphires, tourmalines and topaz. These gems are hard and can withstand great pressure, but they also have the same disadvantage-brittleness, so these gems can't stand knocking and knocking, otherwise they will collapse due to brittleness, or crack or even break along the cleavage direction due to cleavage. 2. Jade jewelry. Although jadeite is hard and tough, it has certain impact resistance. However, the processed jadeite products are often thin and will be damaged by impact. 3. Jade jewelry. Emerald is more brittle than jadeite, and can't stand the impact and beating. In addition, emeralds are afraid of high temperature, which will make their colors fade in case of fire and easily burst at high temperature. 4. Opal jewelry. Opal has low hardness, so it should avoid rubbing against other objects. Opal contains water, so high temperature should be avoided, otherwise it will lose transparency or burst. In addition, opal is not acid-resistant, so wear opal jewelry to avoid high temperature and acidic substances. When collecting opal jewelry, we should also pay attention to the environment not to be too dry, otherwise it will also cause dehydration cracking or even rupture. 5. Amethyst jewelry. The color of amethyst is unstable and will fade when exposed to high temperature or for a long time. Avoid high temperature or exposure during wearing or storage. 6. Malachite and turquoise jewelry. These two kinds of gems are very easy to wear. Their chemical properties are unstable and will be corroded and dissolved in acid. Turquoise is particularly easy to change color at high temperature, even if it is exposed to the sun for a long time and soaked in sweat, it will change color. 7. pearls and coral jewelry. The hardness of pearls and corals is very low, and the surface is easy to lose luster due to friction. Both will be corroded and dissolved by acid. It is easy to sweat in summer, and sweating will also damage the surfaces of pearls and corals and lose their original luster. Powder, perfume and hair cream in cosmetics will also make pearls fade gradually. Pearl ornaments must be washed with clear water before collection, and the storage place must also avoid cosmetics.