SPECIMEN: Fairy Stone Concretion

LOCATION: Morocco

MOHS: 3-3.5

This smooth and sculptural rock may look like it was made by human hands. Some people throughout history have even attributed them to supernatural forces. For example, a Scottish legend says that they’re gifts from fairies. But these aren’t fairy gifts, or even abstract art pieces. They’re a type of mineral-cemented rock called a concretion, and studying how these rocks form tells us all about ancient environments.

There’s a site in Morocco where the presence of calcium carbonate concretions like these help preserve the ancient geological environment exactly as it was. Concretions often grow around a small nucleus, like how an oyster forms pearls around some invading irritant. And in Morocco, those nuclei are sometimes fossils, like ammonites! So these rocks are magical all on their own, no fairies needed.