Star Sapphires are always cut into a Cabochon shape with a high dome. This is the only way that the shining star will be seen from the stone. Cutting star sapphires is often remain very few cutters. Miners and first hand buyers only trust the highly experienced cutters who have years' experience and specialization as the cutter need to strike the balance between the carats, stars and colour.
The star in star Sapphires is caused by a phenomenon called Asterism. When viewed with a single overhead light source star Sapphires will show a six rayed star pattern. In most of the cases the star can be clearly under natural light, but it can also be viewed using a strong source of direct light such as a penlight or a halogen bulb. This pattern is caused by microscopic inclusions created by the internal "silk" (rutile needles) that reflect the light. Unlike the other sapphires star sapphires are not translucent.
【Text by Lakpura™. Images by Google, copyright(s) reserved by original authors.】