Diamonds are mainly divided into natural diamonds and artificial diamonds. For natural diamonds, diamonds originally meant very hard, colorless and transparent, and now they are called minerals such as diamonds. 1866, the first natural diamond in southern Africa was found near the orange river, weighing 2 1.5 carats. The main cause of natural diamond is the high temperature and high pressure produced by volcanic eruption, which makes very carbon substances form the crystal structure of diamond. Natural diamond is an equiaxed mineral formed by elemental carbon crystallization. The common crystal forms of diamonds can be divided into octahedron, rhombic dodecahedron, cube, tetrahedron and hexahedron. Natural diamonds are divided into two types according to their nitrogen or boron content, infrared and ultraviolet absorption spectrum characteristics, and then into type I and type II. On this basis, they are divided into type Ia, type Ib, type IIa and type IIb. Pure diamonds are colorless and transparent. If it contains impurities or structural defects, it will have color, such as yellow, which may be caused by Ti and Fe or structural defects. Type Ib diamond contains paramagnetic nitrogen atoms. Often amber yellow, but this type will appear green when the nitrogen content is high. Type IIb diamond containing boron # makes the crystal usually blue or sky blue # makes the diamond blue. Natural diamond is the hardest natural substance # Its grinding hardness (10000HV) is 1 170 times that of timely and 140 times that of corundum. Diamond has strong wear resistance and low friction coefficient. Its wear resistance is 90 times that of corundum. Although diamonds are hard, they are fragile and easily broken under impact. Diamond is an insulator, but its thermal conductivity is higher than that of silver and copper. Diamond is stable to any acid, even at high temperature.

Diamond does not show any effect, but # diamond is easily eroded in alkali, oxyacid salt and metal melt. However, due to the scarcity and high price of natural diamond, it mainly focuses on the development and application of artificial diamond. There are many methods at present. The first and most classic method is the high temperature and high pressure (HPHT) method, which is also prepared by imitating the production principle of natural diamonds. But at present, chemical vapor deposition method is the best, and the prepared diamond has high purity, mainly including hot filament CVD, microwave plasma CVD, DC CVD and so on. Foreign countries have done a good job in artificial diamonds. The synthetic diamonds made by Apollo Company in the United States have been put into production, and the synthetic diamonds produced by Apollo Company are comparable to natural diamonds.