This is a beautiful piece, and it doesn’t photograph well. This is a Pyritized TORNOCERAS widderi cephalopod. It is a coiled cephalopod related to the modern day Nautilis. This is wonderfully pyritized.
The Tornoceras is 23 mm long by 16 mm wide (.90 x .16 inches). It is set on a square piece of matrix 11 cm by 11 cm (4.33 inches by 4.33 inches)
Arkona, Ontario, Canada