Star sapphires and star rubies have six legs in their stars. The legs should be straight and equally prominent. Ruby stars seldom have a combination of translucent and transparent color and a sharp prominent star. There are ways to tell if it is a natural or synthetic stone. Look on the underside of the stone, if there is an "L" stamped on the bottom it is a "Linde Star" and is synthetic. Check for imperfections in the stone, such as unevenness on the bottom, or stripes and lines of color that show through the top. Most naturals have one or more natural imperfection. Natural star rubies and sapphires typically have one or more of the six legs that are uneven or not all of the six are perfectly straight. If the star doesn't move it is a synthetic stone. Usually the synthetic stars are too perfect.