Color Change vs. Alexandrite-Like
By Gary Roskin, G.G., FGA, Senior Editor -- JCK Online, 3/1/2006 2:00:00 AM
We’ve seen some gem materials at gem shows and on home-shopping TV that change color in different lighting, which are sometimes called “alexandrite-like” and other times “color change.” What’s the difference?
Alexandrite is famous for dramatically changing from a medium-dark vivid green in daylight (or daylight-equivalent fluorescent light) to a medium-dark vivid red or sometimes purplish red under candlelight (or incandescent light). Top Russian alexandrite is reportedly closer to a pure green-to-red change, while Brazilian alexandrite switch hits from bluish green to purplish red. Both are extremely rare and valuable.
In years past, any gem material that exhibited similar color change was called “alexandrite-like.” But because gemologists encountered different color changes for gem materials other than chrysoberyl, the term “alexandrite-like” was phased out for an all-inclusive term, “color change.”
The color-change family includes numerous natural and synthetic gems. The most common imitation of alexandrite is synthetic corundum. Synthetic alexandrite-like sapphire has a color change that is typically more bluish in fluorescent lighting, and more purplish in incandescent. Some natural sapphires also show a change of color, and while they do not go from green to red like alexandrite, they are closer to natural alexandrite than the synthetic corundum.
As for what you’ve seen recently, it could be a lab-created material called “zandrite,” which is being increasingly featured on TV shopping networks. Obviously, the marketing gurus who named this gem wanted to link it to alexandrite, even though the colors do not come close to the true alexandrite change.
Or you might have seen the newest color-change gem on the market, zultanite, whose gemological name is “color change diaspore.” The name zultanite honors the 36 sultans of the Ottoman Empire—today’s Turkey—whence the gem originates.
Gem-quality color-change zultanite crystals were first reported in the early 1980s. And while some jewelers were able to find small pieces during the 1990s, fine-quality crystals remained a collector’s item until last year.
Zultanite is transparent and usually eye-clean, with some inclusions under magnification.
Murat Akgun, Zultanite Gems, Fort Lauderdale, Fla., says, “At their best, the stones turn from kiwi-like green to rhodolite-like purplish pink. The same stone can show a khaki green to brownish pink color change in a different environment. It might shift from a light, pinkish champagne color to that of ginger ale under different light sources. You will witness the kiwi-like green easily when viewed outdoors except under direct sunlight.
“Yellow flashes will be noticeable under sunny skies,” he continues. “You will see a rich champagne color when you view the same stone under regular light bulbs used indoors. The same zultanite will show you its pink and purplish hues in a romantic restaurant with candlelight.”
The only known source for this material is a remote location in Turkey.
Wholesale prices range from $100 to $1,000 per carat for the regular shapes and sizes and up to $5,000 per carat for stones over 10 carats. Expect to pay more for matched pairs, sets, and special shapes.
Final note: Many gems exhibit a slight color shift when viewed under different light sources, but if the color differences are not pronounced enough, it is common for suppliers to ignore it. Unless you want your client to find out for himself that his gem’s appearance outdoors differs from its appearance indoors, you should take the initiative and test every gemstone in stock before a sale.
