June 23, 2016

The Alexandrite

Alexandrite Gemstone – Color Changing Birthstone

Photo by accessgems.com

Half of the months in the calendar year—March, June, August, October, November, and December—have more than one “official” birthstone. June has three choices: pearl, the most traditional, alexandrite and moonstone. My June favorite is alexandrite, which has a distinctive color-change phenomenon. Indoors, it appears red but in sunlight it appears green, which is why gem aficionados often describe it as “emerald by day, ruby by night.”

But in 1912, the American National Retail Jewelers Association, a trade organization now known as Jewelers of America, created the modern American birthstone list. At that time, aquamarine was designated the official birthstone for March; pearl was designated for June, and peridot for August. The list was updated in 1952, adding alexandrite and moonstone as options for June, tourmaline as an option for October, citrine as an option for November, and zircon for December. The official list expanded again in 2002, when Tanzanite was made an additional December birthstone—and again just this year, adding spinel for August.

Cushion-Cut Brazilian Alexandrite & Diamond Ring

2.75-ct cushion-cut Brazilian alexandrite, color changing from bluish-green to purple, set in platinum with 152 microset diamonds, and amethyst, garnet and sapphire accents. Additional alexandrites of 0.04 ctw.

Alexandrite is a very rare variety of the mineral chrysoberyl. Originally discovered in Russia’s Ural Mountains in the 1830s, alexandrite now is found in Sri Lanka, East Africa, and Brazil. The original Ural Mountain deposits are gone, though occasionally some old Ural material turns up in estate jewelry or antique Russian jewelry. Luckily, a 1987 deposit discovered in Hematita, Minas Gerais, Brazil proved to have high quality alexandrite, and much of the best new material comes from Brazil. But very fine stones—the kind that appear bluish green and purplish red without any traces of brown or gray—still are exceptionally rare and valuable.

Alexandrite & Diamond Oval Ring

Alexandrite & diamond oval ring set in 18K white gold; 14 fancy shape alexandrites weighing 4.55cts, accented with 541 round diamonds weighing 2.81cts.

 

As I mentioned earlier, alexandrite looks green in daylight—and also in fluorescent light—and appears red in incandescent light or candlelight. This color-change phenomenon is due to the unusual way the crystals absorb the yellow portion of the white light spectrum, as well as the stone’s chemical composition of iron, titanium, and chromium, the element responsible for the color change.

Cushion-Cut Green Color Changing Alexandrite

An 8.82 ct. cushion-cut color-change alexandrite is green in daylight. From the Dr. Eduard J. Gübelin Collection, courtesy Gemological Institute of America. Photo by Robert Weldon, © GIA.

Cushion-Cut Alexandrite Ruby-Purple Color

An 8.82 ct. cushion-cut color-change alexandrite is reddish purple in incandescent light. From the Dr. Eduard J. Gübelin Collection, courtesy Gemological Institute of America. Photo by Robert Weldon, © GIA.

 

When the gem was first discovered near the Tokovaya River in the Urals, it was named for Czar Alexander II, heir apparent to the Russian throne, as the red and green colors of the stone mirrored the principal colors of old Imperial Russia.

Cushion-Cut Alexandrite from Ural Mountains in Russia

2.85 ct. cushion-cut alexandrite from the Ural Mountains, Russia. Part of the Dr. Eduard J. Gübelin Collection, courtesy Gemological Institute of America. Photo by Robert Weldon, © GIA