"Emerald by Day, Ruby by Night"
Alexandrite is one of the most extraordinary gems in the world: it appears green or bluish-green in daylight and red or purplish-red under incandescent (lamp) light. This dramatic colour change made it legendary. It is a rare variety of chrysoberyl (Mohs 8.5), and Sri Lanka is one of the few significant sources, producing stones renowned for a strong, clean change.
How the Colour Change Works
Trace amounts of chromium cause the crystal to absorb light unevenly. Under daylight (rich in blue/green), the stone looks green; under lamplight (rich in red), it looks red. The phenomenon is so associated with this gem that the effect itself is called the "alexandrite effect."
What Affects Value
- Strength of colour change — a dramatic, complete shift from green to red is most valuable.
- Colour quality — vivid colours in both lighting conditions.
- Clarity & carat — clean stones are rare, and large alexandrites are exceptionally so.
Fine alexandrite is among the most expensive coloured gemstones, often rarer than diamond in good sizes.
Buying Tip
Test the colour change yourself under both natural daylight and a warm incandescent bulb, and always get certification. See our buyer's guide.
See the Source
Browse Ratnapura accommodation to explore the gem country where alexandrite is found.