While Russia is the most famous alexandrite source, this stone from Brazil shows beautiful color change from daylight (left) to incandescent light (right). - © GIA & Tino Hammid, courtesy Mayer & Watt
Fine alexandrite is green to bluish green in daylight and red to purplish red in incandescent light. Its color saturation is moderately strong to strong. Stones that are too light do not reach the quality of color intensity seen in fine-quality gems. Stones that are too dark lack brightness and appear almost black.
Production from Russian mines is very limited today, which means the intense, fine-colored gems they produced in quantity less than 200 years ago are much harder to come by.
Sri Lankan alexandrites are generally larger than their Russian counterparts, but their colors tend to be less desirable. The greens tend to be yellowish compared to the blue-green of the Russian stones, and the reds of Sri Lankan alexandrite are typically brownish red rather than purplish red.
This color-change alexandrite has low saturation in both its green and red colors, making it slightly brownish and less desirable. - Alan Jobbins
The color change displayed by this alexandrite from Sri Lanka lacks strength, and its colors are brownish.
Alexandrites from Brazil have been found in colors that rival the Russian material, but production from Brazil has decreased.
Currently, alexandrite supply is low, and fine-color material is extremely rare.
Alexandrite tends to contain few inclusions. There’s a dramatic rise in value for clean material with good color change and strong colors.
A high clarity rating raises the value of alexandrite, especially one with nice color change like this green to red-purple example.
When certain types of long, thin inclusions are oriented parallel to each other, they can create an additional phenomenon called chatoyancy, or the cat’s-eye effect, increasing the alexandrite’s value.
Cat’s-eye alexandrite, with beautiful chatoyancy along with color change, is extremely rare.
Alexandrites are most commonly fashioned into what are called mixed cuts, which have brilliant-cut crowns and step-cut pavilions. Brilliant cuts have kite-shaped and triangular facets, while step cuts have concentric rows of parallel facets.
This alexandrite has stunning color change with intense colors, and very clean clarity. It’s an oval mixed cut, which is common for alexandrite. - Courtesy Evan Caplan Fine Gemstones
Alexandrite’s pleochroism makes it a challenge for cutters. When fashioning alexandrite, cutters orient the gem to show the strongest color change through the crown. It’s crucial to position the rough so the fashioned stone shows both purplish red and green pleochroic colors face-up.
Most fashioned alexandrites are small, weighing less than one carat. Larger sizes and better qualities rise in price dramatically.
This 8.82-carat cushion-shaped alexandrite shows nice color change. Its large size is rare for this stone.
Attractive alexandrites used in jewelry are usually under a carat. This stone is a 0.65-carat triangular-shaped.