Star Sapphire is named "Blue Star". The stone is produced in Sri Lanka. The original stone weighs 162.5 carats. After grinding, the gemstone weighs 67.98 carats. It is indigo in daylight. There is no blemishes, full transparency, perfect starlight, flexibility, clarity and brightness. Even more surprising is the "color-changing star sapphire" which is blue under a white light source, purple under a yellow light source, and red under ultraviolet light.
A major discovery of the use of UV light to identify discolored gemstones is that discolored gemstones, whether faceted or curved, exhibit a red phenomenon under high-energy UV light irradiation, due to the presence of chromium in discolored gemstones. Chromium ion is reflected from the inside of the gemstone by the energy light source, so the gemstone is red.