In gemology, inclusions are foreign material such as crystals, fluids, or gasses that get trapped inside a mineral while it is being formed. Sometimes inclusions are so small they require a microscope to see. In contrast to external flaws, which are usually the result of some environmental factor, inclusions are internal; they can be solid, liquid, gaseous, or optical. Not all inclusions negatively affect the value of a gemstone. For example, the value of sapphires, rubies, and garnets can be enhanced by inclusions.
