Often described by gem aficionados as “emerald by day, ruby by night,” alexandrite is the very rare color-change variety of the mineral chrysoberyl. Originally discovered in Russia’s Ural Mountains in the 1830s, it’s now found in Sri Lanka, East Africa, and Brazil, but fine material is exceptionally rare and valuable.

Jan 31, 2020 · The geographic source of this rare color-change gem has a significant impact on value. Trace element chemistry profiles allow GIA to accurately determine origin for alexandrite from several countries.

This beautiful butterfly pin has a Russian alexandrite as its body. Its eyes are also alexandrite and they are from Tanzania. The wings have diamonds and other gems from Tanzania and Madagascar. - Photo by Robert Weldon/GIA, courtesy Buzz Gray and Bernadine Johnston

Alexandrite is the rare variety of the mineral chrysoberyl that changes color in different lighting. Most prized are those alexandrite birthstones that show a vivid green to bluish green in daylight or fluorescent light, and an intense red to purplish red in incandescent light.

Abundant alexandrite deposits were first discovered in 1830 in Russia’s Ural Mountains. Those first alexandrites were of very fine quality and displayed vivid hues and dramatic color change.

This 7.19-carat alexandrite was cut to feature its beautiful color change. When the light source changes from daylight to incandescent light, the gem’s color changes from bluish green to reddish purple. Alexandrite, with its chameleon-like qualities, is a rare variety of the mineral chrysoberyl.

The design also features alexandrite and diamond melee accents. The image on the left was photographed with daylight-equivalent lighting and the image on the right with incan-descent light. Pinpoint light was used to reveal the stones’ chatoyancy. Photos …

Alexandrite’s amazing colors are bluish green in daylight and purplish red under lamplight or candle flame.

This inclusion is a hollow space within a gem, called a negative crystal. It’s the same shape as the crystal structure of the alexandrite that surrounds it, and it contains a liquid and a gas. - Photo by Dr. E. J. Gübelin/GIA

Figure 2. Close-up view distinctively pointing out the locations of the crystals (blue arrows) and gas bubbles (white arrows). Photomicrograph by Jamie Price. crystals present, the overall appearance of this alexandrite’s multiphase inclusion is comparable to the typical jagged three-phase inclusions that are distinctive for Colombian emerald.