Chouteau

Chouteau chert outcrops in the chouteau formation ( Meyer 1970).  The Chouteau  limestone formation is of early Mississippian age (Willman 1975), and outcrops in Illinois near Grafton.  Chouteau's Color has been described as "light-to-medium-grey" (Kelly 1984), "molted bluish grey" (Meyer 1970).  The molting that appears in Chouteau chert is irregular producing dark and light spots. Because of small fossils found in this chert, it can also have a speckled look.  Texture ranges from course to fine grained.  Chouteau occurs in tabular or lenticular form with a thick white Cortex (Ray 1989).

The exterior of this piece of Chouteau has been weathered, but it still shows the mottles that are common characteristics of Chouteau chert.

The dark specks on this piece of Chouteau chert are fossil inclusion within the chert.

Notice the cortex (the white area) on top of this piece of Chouteau chert.  The cortex of Chouteau chert  is generally light in color and forms on the exterior edge of  the chert durring formation.

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