Heating yellow, light yellow, or colorless sapphire from 1500-1900oc can turn into a dark yellow, gold, golden brown, orange, or a reddish brown colored sapphire. There is a specific kind of sapphire called Star sapphires have whitish pieces of rutile or silk as some call it. Star sapphires can be heated to remove the blue color of sapphire and can be heated even more to get the blue color back and remove the white silk.