Hexagonaria
percarinata
The “official “state stone” of Michigan is the Petoskey
Stone, the local name for rounded pebbles or cobbles of the fossil coral Hexagonaria
percarinata Stumm, 1969. Petoskey Stones have been weathered &
eroded from fossiliferous limestones of the Traverse Group (Middle
Devonian). They are particularly common in the vicinity of Little
Traverse Bay & the town of Petoskey (northwestern Lower Peninsula of
Michigan).
Beach & lake gravel in this area consists of many
lithologies, including fossiliferous limestone clasts and worn fossil corals
(favositids & colonial rugosans). Hexagonaria is a colonial
rugose coral (Animalia, Cnidaria, Anthozoa, Rugosa, Phillipsastraeidae).
Hexagonaria percarinata (field of view 3.2 cm across) - “Petoskey Stone”.
Hexagonaria percarinata (field of view 2.6 cm across) - “Petoskey Stone”.
The city of Petoskey, Michigan gets its name from an
old Ottawa Indian Chief, Ignatius Petosega. “Pet-o-sega” means “rays of
the rising sun”. Petoskey Stones are so-named in reference to the
dark-colored “eye” & radiating lines of individual Hexagonaria
corallites.