Emerald

Tap it to send green light spiraling around its steps.

An emerald is a green form of the mineral beryl, colored by tiny amounts of chromium or vanadium. Most emeralds have little specks and cracks inside them, and jewelers often cut them in rows of long, flat steps. That shape is so common for emeralds that it is called the emerald cut.

A step cut works like a hall of mirrors. Tap it and green light races around the edges of the steps, each one a moment behind the one outside it, so the light spirals in to the flat top, the table. Some of the finest emeralds come from Colombia.