A gemstone is a precious or a semi-precious stone used in jewelry. Gemologists identify gemstones. They label gems in the arena of gemology using practical language and their features. A gemologist uses the gemstone’s chemical arrangement to classify it. For instance, diamonds are made of carbon (C). Many gems are categorized by a crystal system because they are crystals. Gemstones are classified into different varieties, species, and groups. They are also characterized in terms of dispersion, hardness, specific gravity, refractive index, luster, fracture, and cleavage. Flaws in a stone are known as inclusions.