What are Sri Lankan Alexandrite stones?

Sri Lankan Alexandrite is a super rare and very valuable form of chrysoberyl. It is known for that striking optical behaviour where it can swap colour based on the ambient lighting. Honestly, it is among the most expensive gemstones around, and it will often beat diamonds in value.

In natural daylight, or even under fluorescent lamps, a top-grade Alexandrite tends to look emerald green or maybe a bluish-green tone. But once you place it near incandescent indoor lighting, or around candlelight, the stone clearly changes direction, going towards a purplish-red or a raspberry-red appearance. It has been described for years as “emerald by day, ruby by night”, and the best Sri Lankan pieces are intensely wanted by high-end collectors and people who invest in rare stones.