Alexandrite
The chameleon gem, green in daylight, red under incandescent light.
Alexandrite is the color-change variety of chrysoberyl, famous for its remarkable ability to shift from bluish-green in daylight to purplish-red under incandescent light. First discovered in Russia's Ural Mountains in 1830, it was named after Czar Alexander II. Fine alexandrite with strong, clean color change is among the rarest and most expensive gemstones in the world, often exceeding ruby and emerald in per-carat price. The phenomenon is caused by chromium impurities that absorb specific wavelengths differently depending on the light source.
What are the properties of alexandrite?
| Hardness (Mohs) | 8.5 |
| Refractive Index | 1.746–1.755 |
| Specific Gravity | 3.73 |
| Crystal System | Orthorhombic |
| Chemical Formula | BeAl₂O₄ (with Cr) |
Color Varieties
Major Sources
Brazil · Sri Lanka · East Africa · Russia (historical, mostly depleted) · India
What affects alexandrite price?
Color Change Strength
The more dramatic and complete the color change, the higher the value. A stone that shifts 100% from green to red is exponentially more valuable than one showing partial change.
Color Quality
The best stones show vivid bluish-green in daylight and vivid purplish-red in incandescent light, without brownish or grayish modifiers.
Size
Fine alexandrites over 1 carat are rare. Stones over 3 carats with strong color change are museum-quality pieces.
Origin
Russian alexandrites carry the highest premiums due to historical significance and superior color change, though fine Brazilian material is also highly valued.
How much does alexandrite cost per carat?
Retail prices as of mid-2026. Actual cost depends on color, clarity, origin, and treatment.
| Quality | Price/ct | Notes |
|---|---|---|
| Moderate color change (<0.5ct) | $1,000–$3,000/ct | Weak to moderate color shift |
| Good color change (0.5-1ct) | $5,000–$15,000/ct | Clear green-to-red shift |
| Strong change (1-3ct) | $10,000–$30,000/ct | Vivid color change, eye-clean |
| Exceptional (3ct+) | $25,000–$70,000+/ct | Museum-grade color change |
| Lab-created | $5–$500/ct | Same optical effect, fraction of the cost |
How to care for alexandrite
Do
- Clean with warm soapy water and a soft brush
- Safe for ultrasonic cleaning in most cases
- Store separately to avoid scratching softer stones
Don't
- Don't expose to extreme heat
- Avoid harsh chemicals
- Don't buy without viewing under both daylight and incandescent light
Cleaning Method
Warm soapy water is the safest method. Ultrasonic is generally safe for untreated alexandrite.
How to buy alexandrite
Always view alexandrite under both daylight-equivalent and incandescent lighting before purchasing.
Be extremely cautious of 'alexandrite' sold at low prices. Most is actually synthetic or color-change sapphire.
Lab-grown alexandrite exists and is significantly cheaper. Demand a lab report for natural origin.
Expect to pay more per carat than ruby or sapphire for fine natural alexandrite with strong color change.
Brazilian alexandrite offers the best availability of fine material. Russian stones are essentially all vintage.
Did You Know?
Alexandrite was discovered on the same day Czar Alexander II came of age, and its red/green colors matched Russia's military colors.
Fine alexandrite was described as 'emerald by day, ruby by night.'
A 65.7-carat alexandrite in the Smithsonian is the largest faceted example on public display.
Frequently asked questions
Why is alexandrite so expensive?
Natural alexandrite with strong color change is roughly 8,000 times rarer than diamond in fine quality. Most rough produces weak or partial shifts, and stones over 1 carat with vivid green-to-red change are genuinely scarce. That supply constraint drives per-carat prices above ruby and emerald at equivalent quality tiers.
How does alexandrite color change work?
Chromium impurities absorb light differently depending on the light source. In daylight or fluorescent light, the stone appears bluish-green. Under incandescent or candlelight, it shifts to purplish-red. The effect is called the alexandrite effect, and stronger, more complete shifts command exponentially higher prices.
Natural vs lab alexandrite: what is the difference?
Lab-grown alexandrite (flux or Czochralski) replicates the same color-change optical effect at $5 to $500 per carat, as of mid-2026. Natural stones with comparable color change start around $5,000 per carat. Lab material is chemically and optically similar but lacks the rarity premium and investment appeal of certified natural origin.
Is alexandrite good for engagement rings?
It can work, but with caveats. At 8.5 Mohs, alexandrite is harder than emerald and most semi-precious stones, though softer than sapphire or diamond. A bezel or protective setting is wise. The color-change effect also makes the ring look different indoors versus outdoors, which some wearers love and others find unpredictable.
What is the best alexandrite origin?
Russian Ural Mountain alexandrite carries the highest historical premium for its strong, clean color change, though the deposit is essentially depleted. Brazilian alexandrite is the primary source of fine material today. Sri Lankan and East African stones vary widely in color change strength; origin matters less than the quality of the shift itself.
Related Resources
Related Gemstones
Garnet
A family of gems spanning every color, not just the deep reds.
Sapphire
Corundum in every color except red, the most versatile precious stone.
Spinel
The great imposter, historically mistaken for ruby and sapphire, now prized in its own right.
Tourmaline
The rainbow gem. No other mineral occurs in as many colors.
Comparisons
Last updated: 2026-08-12