Most collections in NW PA and NE Ohio contain, to some degree, Onondaga Chert. Onondaga was brought to this region by the glaciers.
DeRegnaucourt and Georgiady give the following info and description from "Prehistoric Chert Types of the Midwest"
GEOLOGICAL STRATIGRAPHY Edgcliff, Nedrow/Clarence, and Moorehouse members of the Onondaga Limestone Formation of the Early to Middle Devonian System.
OUTCROP LOCATION OR CHERT SOURCE Onondaga is found in escarpment quarries and glacial drift in the Niagara Falls region of western New York and Ontario. The best source is along the Lake Erie shoreline in the province of Ontario extending from Fort Erie westward and also along Lake Erie and the Niagara River on the southern Lake Erie shoreline.
NATURALLY OCCURING FORM OF CHERT Found as nodular and tabular chert within it's parent limestone matrix. It is often weathered out in small pebbles in the streambeds.
COLOR The most common color is dark grey. Mottling often occurs with a lighter grey speckled with darker blue-grey including tans and browns. Heat treatment shows little change in coloration and the material becomes less knappable. Munsell colors are N4 thru N7 inclusive, 10YR 6/6, 10YR 6/1, 10 YR 5/1, 5YR 2/1, and 5Y 8/1.
MINERALS PRESENT Limonite, hematite, dolomite, cryptocrystalline quartz.
FOSSILS Various fossils have proven to be diagnostic for this chert.
*Onondaga was used throughout all prehistoric time periods in this area. Below are several examples.
DeRegnaucourt and Georgiady give the following info and description from "Prehistoric Chert Types of the Midwest"
GEOLOGICAL STRATIGRAPHY Edgcliff, Nedrow/Clarence, and Moorehouse members of the Onondaga Limestone Formation of the Early to Middle Devonian System.
OUTCROP LOCATION OR CHERT SOURCE Onondaga is found in escarpment quarries and glacial drift in the Niagara Falls region of western New York and Ontario. The best source is along the Lake Erie shoreline in the province of Ontario extending from Fort Erie westward and also along Lake Erie and the Niagara River on the southern Lake Erie shoreline.
NATURALLY OCCURING FORM OF CHERT Found as nodular and tabular chert within it's parent limestone matrix. It is often weathered out in small pebbles in the streambeds.
COLOR The most common color is dark grey. Mottling often occurs with a lighter grey speckled with darker blue-grey including tans and browns. Heat treatment shows little change in coloration and the material becomes less knappable. Munsell colors are N4 thru N7 inclusive, 10YR 6/6, 10YR 6/1, 10 YR 5/1, 5YR 2/1, and 5Y 8/1.
MINERALS PRESENT Limonite, hematite, dolomite, cryptocrystalline quartz.
FOSSILS Various fossils have proven to be diagnostic for this chert.
*Onondaga was used throughout all prehistoric time periods in this area. Below are several examples.
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