Materials Science

What causes the rainbow shimmer of ammolite gems?

The colorful flair of ammolite jewelry comes down to crystalline thickness and spacing

An ammolite fossil with lots of different shimmering opal-like colors in oranges and greens

Ammolite gems are some pretty fabulous fossils. Their rainbow flair comes down to nanoscale features in their crystal plates.

Hiroaki Imai

By Maria Temming

The jewels nabbed in the Louvre heist may still be at large, but scientists have just closed the case on another gemstone mystery: what gives rare ammolite gems their rainbow shimmer.