If a gem is not beautiful, it can't be a gem. This kind of beauty is either colorful, transparent and clean, or has special optical effects (such as cat's eye, color change, night light, etc.). ), or have special patterns (such as chrysanthemum stone, agate, plum blossom jade, etc. For example, diamonds with few defects can be polished into precious diamonds, while those with poor transparency, many defects and black color can only be used as industrial raw materials.
Because of its high value, people must expect it to be durable, valuable and even heritable. One of the reasons why diamond is the most expensive gem is that it is the hardest in the world and is not afraid of corrosion. Therefore, most of the gems in the world are silicate minerals with high hardness and corrosion resistance (such as jadeite), a few oxides (such as rubies and sapphires) and elemental minerals (such as diamonds).