Jewelry is a general term for pearls and precious stones. Pearl is a beautiful round object with luster, which is gradually formed by pearlite secreted by sand microorganisms when they enter the shell of shellfish. The chemical composition is calcium carbonate and a small amount of organic matter, which is not only used as an ornament, but also has medicinal value. Generally speaking, gems are precious minerals with hardness above 7 degrees and beautiful colors, which will not undergo chemical changes due to the action of the atmosphere and drugs, and the output is scarce. Excellent performance such as: diamonds, jadeite, beryl jade, precious garnet, tourmaline, precious opal, etc. The quality is slightly inferior: crystal, chalcedony, agate, jasper, malachite, amber, garnet, opal and so on. Here are the chemical compositions of some common gems: diamond, also known as king kong, commonly known as Jin Gangzuan, diamond or diamond, is an allotrope of carbon with a hardness of 10, and is the hardest mineral. Synthetic diamonds are also called synthetic diamonds. Corundum is a transparent crystal with a hardness of 9, second only to diamond. Its main component is Al2O3, and some are colorless, red, blue and Xing Cai. Colorless and transparent is also called white jade; Blue containing Ti( = 4 * Rome IV) or Fe( = 2 * Rome II) and Fe( = 3 * Rome III) is called sapphire. Red containing Cr( = 3 * Rome III) is called ruby, also called ruby; Xing Cai's face is also known as the jewel of Xing Cai. Beryl, also known as emeralds and emeralds, is a transparent to translucent crystal with a hardness of 7, mostly emeralds, light green, colorless or blue, yellow, white and pink, and its main component is 3BeO Al2O3 6SiO2. Among them, the green color with CrO3 is called green column jade, also called emerald or emerald; Iron is transparent blue and is called aquamarine; Rose containing cesium is called rose soul beryl. Topaz, also known as topaz, is similar to crystal in appearance, often yellow and transparent, with hardness of 8, and its main chemical composition is Al2[SiO4](F, OH)2. Jadeite and nephrite, commonly known as jadeite, are composed of NaAl(SiO3)2, which is crystalline or dense, with strong green, light green or white. Green jadeite is often called jadeite, which is slightly transparent and has a hardness of 6.5 ~ 7, which is more difficult to dissolve than nephrite. The composition of nephrite is Ca(Mg, Fe)3(SiO3)4, and its hardness is 5.5 ~ 6. Garnet is a fluorosilicate with unknown composition and the molecular formula is as follows: 0? 4O3 3SO2, where R stands for calcium, magnesium, iron or manganese, and also stands for aluminum, iron, chromium or cobalt, has a hardness of 6.5-7.5, is transparent to slightly transparent, and sometimes has abnormal optical properties, showing birefringence and beautiful color shift. The composition of Fe3Al2Si3O 12 is called Guigarnet, which is usually red or pink with a slightly black appearance. Opal contains water and silica, and its hardness is not as good as that of time. Its surface is often grape-shaped, with white ash, yellow brown and other colors, shiny like fat or pearls, opaque to slightly transparent. If it is beautiful breast-shaped, often red or green, with strong luster, and the cross section can reflect various beautiful colors, it is often called precious opal. The crystal is hexagonal columnar pure-time crystal, colorless and transparent, with large refractive index. The internal mechanism is that those with smoky pottery color are called smoky crystals (commonly known as tea crystals) and those with black color are smoky crystals (commonly known as mo crystals). Nitrogen-containing organic matter is brown or yellow, which is called brown timely or topaz. Those with manganese and purple are called amethysts. Chalcedony is transparent or translucent, and its composition is SiO2, and its hardness is 7. There are meat red, light red, dark green, blood red and so on. Opaque is agate. Jasper is deposited by siliceous substances, and its chemical components are SiO2 _ 2 and Fe2O3. Because it contains iron, various colors often appear. Its dark green chalcedony is very similar to dark green chalcedony, dense and opaque. Amber is composed of hydrocarbons (C 10H 16O), amorphous, transparent to translucent, reddish brown, with hardness of 2-2.5, and can generate electricity by friction. Malachite is composed of Cu2(OH)2CO3, which is formed by copper-bearing minerals under the action of carbonic acid and water. Its luster is like a diamond, its color is green, and occasionally it has a twisted peacock tail.