Gemology: the science dealing with natural and artificial gemstone materials. It is considered a geoscience and a branch of mineralogy. Some jewelers are academically trained gemologists and are qualified to identify and evaluate gems. When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal characteristics under magnification.