Oneota Chert



2003 by the Center For Social Research, Parkland College



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TEXTURE:
The texture is typically medium, but both coarse and fine grained material can be found. The majority of stone artifacts will be fashioned from the finer grained material.

LUSTER:
Luster tends to be dull to waxy.

COLOR:
The base color will typically be white to gray to yellowish and orange. Contrasting shades of banding may occur. The characteristic oolites will be in contrasting shades of the background color.

FOSSILS:
Fossils are unidentified but present in small quantities.

STRUCTURAL CHARACTERISTICS:
Note the presence of a few small (less than 0.8 mm) oolites (Ferguson and Warren 1992: 30). If you go to the large image of the illustration you will observe that the matrix includes a few "spots" and "doughnuts." The "spots" are the whole oolite. The "doughnuts" are where the oolite has been split revealing a center of contrasting color.

Shakopee Chert is also oolitic, but they will be larger and far more numerous.

Note in the top illustration the presence of a quartz filled parting or seam in the upper right hand corner. Also note the small, circular, brown spots ("freckles") near the top and center of this object. The "freckles" are fossiliferous voids lined with iron oxides (rust).

HEAT TREATMENT:
Oneota Chert was frequently heat treated. Colors change to grayish pink, yellow, orangish gray, pink, and red. Iron rich elements become orange to red. Luster becomes glossy. The upper illustration is heat treated.

SOURCE:
The upper illustrated specimen was recovered from the Grand Village of the Illinois state historic site, LaSalle County, Illinois. In this locale the chert is often referred to as "Starved Rock Chert." The lower illustrated specimen was generously provided by Jacquelin Ferguson and Robert Warren of the Illinois State Museum. It was recovered from a natural stratum at the Utica Quarry just south of the town of Utica, LaSalle County, Illinois.




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