Highly polished fossilised coral tumbled stones from the area around Lake Michigan. Most 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 very finest grade of stone 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. The cup which is secreted by the polyp is aragonite which is the crystalline form of calcium carbonate. This chemical compound occurs in rocks and the minerals calcium and aragonite. It's also the main component of eggshells, snail and seashells and pearls.
This variety of fossilised coral is widely known as Petoskey Stone. The name comes from the city of Petoskey after which it was named. Petoskey Stone became the official stone of the state of Michigan in 1965.
These beautifully polished fossilised coral tumbled stones are available in medium and large sizes.