The quirky geology behind Olympic curling stones

By Andrea Thompson – Scientific American

Athletes often have specialized equipment or apparel to make them run, swim, skate or ski their best, but curling takes things to another level. Curling rocks—as the round, roughly 40-pound stones are called—only come from two places on the planet: a little island in Scotland called Ailsa Craig and the Trefor granite quarry in Wales.

But what makes the rocks from these places uniquely suited for sliding across a rectangular slab of ice toward a bullseye target? And are these really the only places to find suitable stones?