Alexandrite

Alexandrite is the color-change variety of chrysoberyl, shifting from green or bluish green in daylight to red or purplish red under incandescent light. The change is caused by chromium in the crystal, not by any treatment.

Yes, and it is the defining test of the species. Chromium absorbs light so that daylight favors the green side and warm lamplight the red side. The stronger and more complete the change, the finer the alexandrite.

Its formation requires chromium and beryllium in the same rock, a combination geology rarely delivers. Historic Russian stones are museum territory, and fine material from Brazil, Sri Lanka, and East Africa remains scarce at every size.

Alexandrite is typically untreated, and the status is stated on every listing. The color change is a property of the crystal itself and cannot be created in natural stone by treatment.

The change comes first: completeness, and the strength of both the green and red states. Clarity, cut, and size follow. A strong change in a smaller stone outranks a weak change in a large one.

Yes. At 8.5 on the Mohs scale, chrysoberyl is harder than any gem except corundum and diamond, and alexandrite suits daily rings without special caution.

Every alexandrite ships with the Sosna Gems Colored Stone Report, our internal documentation. Independent laboratory certification can be arranged on request, and for alexandrite we recommend it as standard practice.

Yes, and with this species it is the usual route: fine alexandrites often change hands before being advertised. Contact us with your parameters and we will search through our channels.

Test the change yourself: daylight window, then a warm lamp. The stone that commits to both colors instead of hovering between them is the better alexandrite, whatever the paperwork says about the rest.