Alexandrite
| Property | Details |
|---|
| Mineral | Chrysoberyl |
| Mohs Hardness | 8.5 |
| Refractive Index | 1.746 – 1.755 |
| Birthstone | June (alternative) |
| Anniversary | 55th |
| Major Sources | Brazil, Sri Lanka, East Africa, Russia (historic) |
| Treatments | Rarely treated |
Overview
Alexandrite is one of the rarest and most fascinating gemstones, prized for its remarkable color-change property. In daylight or fluorescent light it appears green to bluish-green; under incandescent light it shifts to red, purplish-red, or raspberry. The more dramatic the color change, the more valuable the stone.
History & Lore
First discovered in Russia's Ural Mountains in the 1830s, alexandrite was named after Czar Alexander II because it displayed the national military colors of imperial Russia: green and red. The original Russian deposits are now essentially depleted, making old Russian alexandrites extremely collectible. Today, fine alexandrite primarily comes from Brazil, Sri Lanka, and East Africa.
Quality & Value Factors
The strength and completeness of the color change is the primary value driver. An alexandrite that shifts from a vivid green to a vivid red is dramatically more valuable than one showing only a slight shift between muddy colors. Natural alexandrite is extremely rare and expensive—fine stones can exceed the price of rubies and sapphires per carat.
Care & Cleaning
Alexandrite ranks 8.5 on the Mohs scale, making it very durable for all types of jewelry. It can be cleaned safely with warm soapy water or ultrasonic cleaners. Its outstanding hardness and rarity make it an exceptional collector's gemstone and an unconventional but stunning choice for engagement rings.
Frequently Asked Questions
Why does alexandrite change color?
Alexandrite changes color because of the way chromium impurities in the chrysoberyl crystal interact with different types of light. Chromium absorbs light in the yellow portion of the spectrum. In daylight, which is rich in blue and green wavelengths, the stone appears green. Under incandescent light, which is rich in red wavelengths, the stone appears red or purplish-red. This phenomenon is unique to alexandrite and a few other rare gemstones.
How rare is natural alexandrite?
Natural alexandrite is one of the rarest gemstones in the world. The original Russian deposits in the Ural Mountains are essentially depleted. While new sources have been found in Brazil, Sri Lanka, and East Africa, fine-quality stones with strong color change remain extremely scarce. Alexandrite with vivid color change over one carat is genuinely rare, and prices for fine specimens can exceed $70,000 per carat.
Is alexandrite more expensive than diamond?
Fine natural alexandrite can be significantly more expensive than diamond on a per-carat basis. While commercial-grade alexandrite with weak color change is more affordable, top-quality stones with strong green-to-red color change in sizes above one carat routinely sell for $30,000 to $70,000 per carat or more. Exceptional Russian alexandrites have sold at auction for over $100,000 per carat.
What is the relationship between alexandrite and chrysoberyl?
Alexandrite is the color-change variety of the mineral chrysoberyl. The chrysoberyl family also includes cat's eye chrysoberyl (cymophane) and ordinary transparent chrysoberyl. All share the same crystal structure and excellent hardness of 8.5. Alexandrite gets its special color-change property from trace amounts of chromium replacing aluminum in the crystal lattice.
Can alexandrite be used in engagement rings?
Alexandrite makes an excellent engagement ring stone. At 8.5 on the Mohs scale, it is harder than any gemstone except sapphire, ruby, and diamond. It has no cleavage concerns and excellent toughness. The main challenge is finding a natural alexandrite of suitable size and quality, as fine stones are extremely rare and expensive. Lab-created alexandrite is available as a more affordable alternative with identical physical properties.
Specialty & Collector Gemstones