Chrysoberyl - cat's eye gems
Chrysoberyl - cat's eye gems

Cutting Star and Cat's Eye Gems


Learn how to cut star and cat's eye gems. Once you understand how asterism and chatoyancy work, you'll find unexpected treasures in overlooked gem rough.

6 Minute Read

Once, a top collector told me he needed malaya garnet cat's eye gems. Unfortunately, they were “practically nonexistent.” I was able to find several pieces for him with light-reflecting veil inclusions. These pieces were simply overlooked in the search for facetable rough!

Here's what you need to know to start cutting stars and cat's eyes.

What Causes Star and Cat's Eye Effects?

Well-cut star and cat's eye gems are a delight to the eye and great fun to cut. These phenomenal stones display asterism and chatoyancy, respectively. Both effects are the result of light reflecting off inclusions within the gemstones. Although silk (fine included crystals) is the most common cause of these visual phenomena, any inclusions that reflect light in parallel lines can create these displays, including hollow tubes, feathers, and veils.

Considerations for Cutting Star and Cat's Eye Gems

As with any gem, take into account inclusion management, shaping the girdle, etc. For a phenomenal gem, you also want the stone to have a relatively high dome. This will make the star or eye stand out. If the gem's crown is too shallow, the arms will be wide and less bright. If the crown...


Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

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