Asterism is a term which describes “the effect of light rays forming a star (Latin aster, star)…It is usually created through reflection of light by thin fibrous or needle-like inclusions that lie in various directions.” [1]
Stars in gemstones may have four, six, or (less frequently) twelve rays. With these stones, the angle of the stone to a light source is important to be able to see the star. Natural gemstones known to exhibit asterism include:
- star sapphire
- star ruby
- star diopside
- star rose quartz
- star blue quartz
- star garnet
- star spinel
[1] Gemstones of the World: Newly Revised & Expanded Fourth Edition by Walter Schumann, p.52
