A gemstone enhancement that utliizes melted glass or hard plastic that is used to fill cracks, fissures or cavities on the surface of the gemstone. Most often done to poor quality rubies to enhance clarity and luster, glass filling (also known as fracture filling) is not considered a natural treatment, and it must be disclosed as this type of treatment conceals gemstones that could easily fracture or shatter with only light bumps.
See Also: Enhancements, Anneal, Oiling