The specific formation conditions, chemical composition, and internal structure of each gem determine its unique morphological characteristics, physical properties, and chemical properties. At the same time, some gemstones have some similar genesis, chemical composition, or internal structure, that is, have commonness.
Therefore, the task of gem classification is to use a scientific method to reveal and express this kind of commonness and individuality, and to classify a group of gems that are essentially the same and have the same internal law together. However, due to the particularity of the gem itself, there is no unified classification scheme in the world so far.
（Amethyst crystal）
（Aquamarine ore）
For example, in some parts of the world, it is customary to divide gemstones into two categories, namely colored gemstones and diamonds, and in these two categories, natural and synthetic gemstones, etc. Others put pearls in a separate category. Therefore, how to classify gems scientifically and reasonably is a common concern of the international jewelry industry.
（Tourmaline ore）
（Emerald crystals）