Large and highly polished fossilised coral gem grade stone. The colour and markings in this curious material are completely natural. This piece was cut as a cabochon for Stone Mania from a larger rough piece of stone.
Although the front has a vitreous lustre the back has only been lightly polished. It therefore has a dull lustre meaning the surface does not reflect light.
Fossilised coral dates back approximately 350 million years and comes primarily from Indonesia and the shores around Lake Michigan. Stones can be found on beaches and in several other locations but in particular close to the cities of Petoskey and Charlevoix. Stones from this area are widely known as petoskey stone.
The six-sided corallites that can be seen are skeletal cups formed by polyps into which they retracted. Polyps which are related to sea anemones and jellyfish have a sac-like body and '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 as the minerals calcium and aragonite. It's also the main component of eggshells, snail and seashells and pearls.