Of particular interest in the evaluation are natural rubies with the effect of asterism (from the word "aster" - a star). Starlight is caused by the optical effect of microscopic inclusions of needle-like minerals evenly located in the stone.
Asterism in sapphires and rubies is highly valued. Such stones are costly and are in great demand among jewelers. They look outstanding in jewelry combined with diamonds. Such stones cost more than $1,000 per carat. The most essential value of such rubies is their red color. But there are few such stones.
In world practice, special requirements have been developed for rubies and sapphires that have the phenomenon of asterism. When evaluating them, it is necessary to take into account:
-the degree of concentration of the star,
-number of beams,
-the shape of a star,
Recently, grayish-red star rubies have appeared on the market. The color of such stones is not bright, and they look more like pinkish-gray sapphires. But such stones look good in men's rings, and fashion is coming to them now.
It is necessary to know that there are fake star-shaped rubies and sapphires on the market. There are such stones on the wholesale market from about $ 50 per carat. They are also offered by scammers for $ 50-100 per carat. I came across such a case in India and almost bought a fake. But synthetic star-shaped rubies and sapphires have a fragile contrasting star in the center of the stone. In natural gemstones, the principal is usually vaguer.