Glass-filled rubies are a type of treated ruby in which surface-reaching fractures and inclusions are filled with lead glass or other flux-based substances to enhance clarity and appearance. These rubies, often derived from low-grade corundum material, undergo an advanced treatment process that improves their transparency and color, making them appear similar to high-quality natural rubies at a significantly lower price.

Unlike untreated or heat-treated rubies, glass-filled rubies have a lower durability due to the presence of lead glass, which makes them more susceptible to scratches, heat, and chemical damage. They typically exhibit a vibrant red hue, but their color and clarity can be artificially enhanced. Since this treatment significantly alters the gem's composition, glass-filled rubies are considered less valuable than untreated or heat-treated rubies and require special care to maintain their appearance.

In astrology, natural rubies (Manikya) are associated with the Sun (Surya Graha) and are believed to enhance confidence, leadership, and vitality. However, glass-filled rubies are generally not recommended for astrological purposes due to their extensive treatment. While they serve as an affordable alternative for ornamental jewelry, buyers should be aware of their limitations and ensure proper disclosure from sellers when purchasing glass-filled rubies.