How to Tell if Alexandrite Is Real: 5 Proven Tests
Real alexandrite changes color under different light (green/blue in daylight, red/purple under incandescent). Test its hardness (8.5 on Mohs scale), check for inclusions with a loupe, and verify its refractive index (1.74-1.76). Lab certification is the most reliable method. Avoid glass or synthetic imitations with overly vivid or static colors.
Key Visual Signs of Real Alexandrite
- Color Change: Genuine alexandrite shifts emerald green/bluish-green in daylight to raspberry red/purplish-red under incandescent light. Fakes often show dull or no change.
- Clarity: Natural stones have minor inclusions (e.g., silk-like rutile needles). Flawless stones are likely synthetic or glass.
- Pleochroism: Rotate the stone under light-real alexandrite displays 3 distinct color tones (green, orange, purple) from different angles.
DIY Tests to Verify Authenticity
- Light Test: Compare the stone under natural daylight and a 60W incandescent bulb. Real alexandrite changes dramatically; fakes stay similar or shift to brown/yellow.
- Scratch Test: Alexandrite scratches glass (hardness 8.5). Drag it gently across a glass surface-if it leaves a mark, it's likely real. Note: Avoid damaging the stone.
- Loupe Inspection: Use a 10x jeweler's loupe to spot natural inclusions. Lab-created stones may have gas bubbles (glass) or perfect clarity (synthetic).
- UV Light Test: Some real alexandrite glows red or purple under UV light, but this isn't foolproof-some fakes mimic this.
Comparison: Real Alexandrite vs. Fakes
| Feature | Natural Alexandrite | Synthetic Alexandrite | Glass/CZ Imitation |
|---|---|---|---|
| Color Change | Strong (green → red/purple) | Sharp but may appear overly vivid | Weak or none; often brown/yellow |
| Hardness | 8.5 (scratches glass) | 8.5 (same as natural) | 5-7 (glass) or 8-8.5 (CZ) |
| Inclusions | Minor natural flaws (rutile, silk) | Nearly flawless or curved striae | Bubbles (glass) or clean (CZ) |
| Refractive Index | 1.74-1.76 | 1.74-1.76 (identical) | 1.5-1.7 (glass) or 2.15-2.18 (CZ) |
| Price | $1,000-$15,000+/carat | $50-$500/carat | $5-$50/carat |
When to Seek Professional Verification
- Lab Certification: Reputable gem labs use spectroscopy and refractometry to confirm origin. Ask for a report detailing color change percentage and trace elements (e.g., chromium, vanadium).
- Red Flags: Avoid stones labeled as 'alexandrite-like' (e.g., color-change sapphire or garnet). These are not true alexandrite and sell for far less.
- Seller Transparency: Request origin details (e.g., Russia, Brazil, Sri Lanka). Synthetic alexandrite is often disclosed as 'lab-created' or 'Chatham-flux.'
Common Alexandrite Imitations to Avoid
- Color-Change Glass: Bubbles, low hardness (5-6), and weak color shift (often green to brown).
- Synthetic Corundum: Lab-created sapphire with vanadium doping. Hardness 9 but lacks alexandrite's pleochroism.
- Cubic Zirconia (CZ): Overly brilliant, heavy for its size, and may show orange/blue flashes (dispersion).
- Natural Alternatives: Color-change garnet or spinel mimic the effect but have lower value and different inclusions.