In viewing natural Alexandrite in daylight it should be a green or bluish-green coloration; the closer to emerald green the better. In warm incandescent light, candlelight or tungsten light the color should change to a reddish-purple, purple, or bluish lavender. The closer the color is to a fine ruby the better the gemstone.
The chemical composition of Alexandrite, for those interested is:
Color: Green/blue daylight and fluorescent light
Hardness: 8.5 on the Mohs’s scale
Natural alexandrite is a reflective gem and when scratched across a surface (please don’t try this with your gem) it will leave a white streak. Be wary of so-called “natural alexandrite” that are amethyst or pinkish in daylight and change to a purply color in incandescent light. These are NOT natural mined Alexandrite. Also seen are synthetics that are blue or grayish blue in daylight and change to a purply color.
Natural Alexandrite typically have inclusions which can be better seen under magnification. Normal inclusions can include tiny crystals that look like black spots in the interior of the gem, veil like silky threads throughout a the whole or portion of the gem, or even what may look like tiny elongated tubes. Also seen at times in natural Alexandrite are fissures that resemble white or clear lines that look like a crack in the gem.
Besides color differences, any stone that has what resembles air bubbles throughout is a synthetic or created stone. A dusty like appearance within the stone that appears as a dull layer in one level is another indication of synthetic alexandrite. Streaks that travel in the same direction with one end rounded are typical of created alexandrite. Strong color banding that can be easily seen if a gem is placed on its side on a sheet of white paper (look for lighter and darker coloration in layers or bands) is still another indication of created or synthetic alexandrite.
In the last two or three years color change crysoberyl has been sold as Alexandrite. The color may change from green to yellow or bluish to brick brown. Color change crysoberyl is NOT Alexandrite. The parameters of color within Natural Alexandrite are limited to the colors listed earlier in this article.
Lab grown Alexandrite is also being sold as Natural Alexandrite or even Natural Russian Alexandrite when the lab is located in the USSR. Although a competent lab or gemologist can tell whether the stone is lab grown or natural mined, the differences are too minute for the consumer, so one has to be very careful.
The bottom line is: know the seller’s reputation. Khazargems has a wide variety of Natural Alexandrite mined from the earth- no lab, synthetic or color change crysoberyls are ever sold by us.