Modern heat treatments that remove the silky rutile inclusions improve clarity but at the same time remove the asterism because it is the silky material which is responsible for the asterism and without the silk, there are no stars. Clean stars do not exist! Marketed stars typically range from 1 - 10cts. in size but some stones are much larger. The American Museum of Natural History's collection includes one of the world's largest and most spectacular blue sapphires- the 153ct. Star of India.
Madagascar star sapphires from Ankarana can be very large and frequently display excellent asterism. We photograph our stars with a fiber optic light above the stone and the effect is similar to direct sunlight or a spotlight. The denim blue color of Madagascar Star Sapphires can be quite even except for the crystal growth lines which prove that the stone is natural.
In terms of price and quality, blue star sapphires from Madagascar are incomparable in value. Ceylon and Burma both produce limited quantities of blue stars but although some are better in quality, their prices are normally substantially higher.
Some traditions say that the star sapphire is a stone of destiny, and that its star acts as a guiding light and protects its wearer against evil. To medieval Christians, the three intersecting bands that form the star represented the spiritual virtues of Faith, Hope, and Charity, Today star sapphire provides a phenomenal September birthstone alternative.