Onondaga Chert

Onondaga Chert- occurs in the limestone of the same name, of Middle Devonian age, outcrops from Ontario Canada in the west to as far as Orange County in eastern NY. It occurs in nodules but more often in bedded strata. Colors range from black to every shade of gray, often with blue/gray and/or gray/white mottling. Similiar in appearence to Fort Payne, but is it not found in overlapping areas. It patinates to brown, tan, or yellow due to inclusions of partially silicified limestone. Heavy weathering can cause significant patination with some pieces acquiring an oxidized rind that appears similiar to red Jasper.

 References

 Jim Fisher, and Converse Robert, Ohio Flint Types, 1994 pp. 194