Highly polished fossilised coral tumbled stones from the area around Lake Michigan. Most of the world's fossilised coral comes from Indonesia or the USA.
Fossilised coral dates back approximately 350 million years. During this time the area around Lake Michigan was close to the equator and covered by a warm shallow sea. Hexagonaria percarinata as this extinct form of coral is correctly known, thrived in the tropical reefs.
In the finest grade material six-sided corallites can be seen. Corallites are skeletal cups formed by polyps into which they can retract. Polyps are related to sea anemones and jellyfish. They have a sac-like body and a 'mouth' surrounded by stinging tentacles.