Identification guide · Precious Stones
How to Identify Alexandrite
Alexandrite is usually green in daylight and red in incandescent light with a vitreous luster and is transparent. It has a Mohs hardness of 8.5. It scratches glass, steel and even quartz; only harder gems will mark it. Its streak is white. It is most often confused with Emerald, Chrysoberyl, and Ruby; the tests below separate them.
Alexandrite identification checklist
| Color | Green in daylight, Red in incandescent light | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Vitreous | Fresh surfaces shine like glass; a dull surface usually means weathering, so chip or wet a corner. |
| Transparency | Transparent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 8.5 | It scratches glass, steel and even quartz; only harder gems will mark it. |
| Streak | White | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Good | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.7 | Heavier than it looks (specific gravity about 3.7). |
| Crystal system | Orthorhombic |
Extra tests for Alexandrite
Glass check. Alexandrite shares a glassy luster and conchoidal fracture with man-made glass. Glass sits near Mohs 5.5 and often contains round gas bubbles, so a hardness test and a hand lens separate them.
Alexandrite look-alikes and how to tell them apart
Alexandrite is harder (Mohs 8.5) than Emerald (Mohs 7.5), so Alexandrite will scratch Emerald and not the other way round. It scratches glass, steel and even quartz; only harder gems will mark it. Alexandrite vs Emerald →
Both sit near Mohs 8.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Alexandrite vs Chrysoberyl →
Both sit near Mohs 8.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Alexandrite vs Ruby →
Both sit near Mohs 8.5, so a scratch test alone will not separate them. Lean on luster, streak and heft instead.
Is my Alexandrite real?
- Hardness: real Alexandrite sits at Mohs 8.5. Glass imitations are about 5.5, so genuine Alexandrite scratches glass while a glass fake cannot.
- Bubbles: round gas bubbles under a 10x loupe mean glass or resin, never a natural stone.
- Color: dyed material concentrates color in cracks and pores; look for pigment collecting at the edges of fractures.
- Temperature: natural crystals feel cool and take longer to warm in your hand than plastic or resin.
Field tips
- Check whether the specimen's color and texture match typical Alexandrite examples.
- Use hardness, streak, luster, grain size, and locality together; no single trait is enough for every specimen.
Alexandrite identification FAQ
How can you tell if a rock is Alexandrite?
Check the color (green in daylight and red in incandescent light), the vitreous luster, a Mohs hardness of 8.5 and a white streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Alexandrite?
Alexandrite has a Mohs hardness of 8.5. It scratches glass, steel and even quartz; only harder gems will mark it.
What is the difference between Alexandrite and Emerald?
Alexandrite (Mohs 8.5, vitreous luster) and Emerald (Mohs 7.5, vitreous luster) look alike, but hardness, streak and heft usually separate them. See the full Alexandrite vs Emerald comparison for a side-by-side table.
How do I know if my Alexandrite is real?
Real Alexandrite matches the hardness listed above, shows no round gas bubbles under magnification, and does not concentrate dye in cracks. Glass and resin fakes fail at least one of those checks.
Is Alexandrite worth anything?
Entry-level Alexandrite specimens sell for around $5000, typical collector pieces about $15000, and premium examples $70000 or more depending on size, quality and locality.
What color is Alexandrite?
Alexandrite is most often green in daylight and red in incandescent light. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
