A free gemology reference site
Gemology, gemstones, minerals and more
The Gemstones
Chrysoberyl
Consumer Information
What color is it?: Chrysoberyl occurs in a number of colors. The finest color of chrysoberyl cat's eye as shown above will be a honey color, with a number of browns and yellows interchanging. The transparent chrysoberyl as shown in the photo below will be a combination of green and yellow. While the very rare form of chrysoberyl known as alexandrite will change colors from red to green depending on what type of light you are standing in. Very rare, indeed.
What is the story behind this gemstone?: Chrysoberyl is a distant cousin to an emerald, hence the namechrysoberyl and beryl. Chrysoberyl is a long wearing stone that can occur in a variety of colors and phenomena.
Can I wear it everyday?: Yes. All of the chrysoberyls are very long wearing. Although at the price of most decent quality alexandrites you will probably want to save that one for the prom, special dinner parties, the opera, etc...and not while you are out framing houses. One small chip on an alexandrite could cost thousands to hundreds of thousands of dollars.
Is it expensive?: Yes...and no. Natural alexandrite will be very, very expensive in the finest qualities. Going as high as US$50,000.00 per carat for the best. While a nice greenish/yellow transparent chrysoberyl as shown below will generally sell for a few hundred dollars per carat. (which is why I have one of those and not an alexandrite in the photograph) And chrysoberyl cat's eyes can range from a couple of hundred dollars a carat to tens of thousands per carat.
Is it a birthstone?: Not really. But if you can afford a nice alexandrite who cares about birthstones anyway.
What do I need to know before going shopping?: Be very, very careful where you shop. If you will go back and look at the Synthetic and Imitation Gemstones page you will see that alexandrite has been synthesized. Meaning that it will test just like the natural. Meaning that if you are not careful about where you shop you could wind up spending hundreds of dollars on a stone worth tens of dollars. Don't let this scare you away from a nice chrysoberyl gemstone, though. Qualified independent jewelers who are properly trained in gemology can easily identify synthetic alexandrite from the natural. And can also identify chrysoberyl cat's eye from a lot of the imitations out on the market. So first make sure where you shop, then prepare yourself for a lot of fun. A nice cat's eye will actually open and close as you rotate it under a light as shown by the photographs below. And you can actually see the alexandrite change color if you have a fluorescent and incandescent light with you and simply change one for the other. Few gemstones offer as many varieties of wonderful color and phenomena as chrysoberyl.
General Information
Cat's eye opening and closing as stone is rotated
Source: Russia before the mines played out. Now Brazil.
Chemical: Al2(BeO4)
Formation: Pegmatite dikes
Crystal System: Orthorhombic
Unusual Properties: Cats Eye (Chatoyancy) and Change of Color
Gemological Information
RI: 1.746 - 1.755
Birefringence: .008 + -
Optic Character: B+
Specific Gravity: 3.73 + -
Hardness: 8.5
Transparency: Opaque to TP
Special Identifying Properties and Tests: Chatoyancy, Color Change. Chromium spectrum for alexandrite. Chelsea filter for alexandrite.
Synthetics: Synthetic alexandrite separated by rain type inclusions which I hope to add to this photo page very soon.
Imitations: For many years (since about 1890) synthetic corundum doped with vanadium to give synthetic corundum a color change effect that emulates alexandrite. Colors are not true to natural alexandrite and experienced gemologists should have no trouble separating.