Moonstone

Moonstone shows adularescence — a floating sheet of light that moves across the stone as you turn it. Sri Lanka's Meetiyagoda deposit has produced the finest material in the world for centuries.

The most valuable variety has a blue sheen on a near-transparent body. Moonstone is a 6 to 6.5 on the Mohs scale, so it is best suited to pendants and earrings rather than rings worn daily.