Gem miners in the African country of Zambia recently made a dazzling discovery: an enormous emerald that weighs more than 1 kilogram (2.2 pounds). Most emeralds are smaller than a paper clip. This one is bigger than your hand!

Emeralds are rare and valuable minerals often used in jewelry. These solid materials form when certain substances in Earth’s crust, or rocky outer layer, are heated and pressed together over time. The chemical element chromium makes emeralds green.

The emerald found in Zambia is so big it probably took hundreds of millions of years to grow, says earth scientist Alisha Clark. “There was likely a special environment for this emerald to form.”