Glowstones, which you often see used in fish tanks, are a synthetic aggregate, based on Photoluminescent pigment and synthetic resin. According to Jinan Chenghao Technology, “When exposed to light sources, the photoluminescent pigment within Glowstone becomes chemically excited and will afterglow (i.e. glow in the dark).” The glow is initially very strong, but then slowly dulls over night.
