F914 - This interesting stone is a variety of Calcite and was formed by the fossilization of the coral Hexagonaria.

Fluoresces: Bright Yellow & Purple

Petosky stones are found on many beaches of Lake Michigan and Lake Huron as well as in rock quarries from Traverse City to Alpena.

The honeycomb-patterned stone has a hardness of 4 - 5 and is the official Michigan State Stone.

Under a long wave ultraviolet light these specimens fluoresce a yellowish/cream color with dark brown at the center of the individual coral chambers.