Fascinating Phenomena in Gemstones, Part 2

Blue Star Sapphire

For part 1 of this article, click here.

As we continue our look at the world of phenomenal gemstones, we examine in this part two familiar phenomena, but the actual names are not very familiar – Asterism and Chatoyancy. This is part 2 in a reprint of an article from the American Gem Society seen here.


Asterism, or stars, relates to the four- or six-rayed star pattern of light produced by the fibrous inclusions, elongated needles, or growth tubes in a gemstone. This singular, celestial-like phenomenon is best seen in a gemstone cut en cabochon.


Cat’s Eye Chrysoberyl

Chatoyancy [sha-TOY-an-cee] is also known as “cat’s eye.” Fine needle-like or fibrous inclusions within the gemstone are what causes this effect. Again, stones fashioned as cabochons display this effect the best.

Leave a Reply

You must be logged in to post a comment.