An inclusion is any substance trapped inside a mineral during its formation. Gemstone inclusions can be found in the form of crystals, bubbles of liquid or gas, or even fractures caused by radioactive substances in the host material. Since researchers continually discover new types of inclusions, a comprehensive list is constantly evolving.

To identify and study inclusions in gemstones, a high-quality microscope and proper lighting techniques are essential. With experience, a skilled gemologist can accurately identify various types of inclusions.