Gemstones & stars

Have you ever seen what appears to be a star on a gemstone? What you’ve experienced is an amazing natural phenomenon called asterism, which occurs on certain types of gemstones.

An Eaton & Jones ring, set with a stunning star ruby.

The fascinating star effect is caused by reflections from tiny, needle-like inclusions that are oriented in several specific directions. These inclusions are termed “silk”.

Stars are usually made up of 2, 3, or 6 intersecting bands, resulting in 4, 6, or 12 rays. The most common stars have 6 rays, and 12-rayed stars are quite rare. ​

A star sapphire's reflection creates an asterism

 Star sapphires & rubies must be cut as a cabochon (polished, not faceted) to display asterism. The value of a star gemstone depends on the clarity of the star. The best and most expensive star corundum is semi-transparent, with just enough silk to create a well-defined, central star.

We have a particularly mesmerising star ruby in our shop window currently, set in a beautiful handmade 18ct yellow gold ring. Pop by to see it!