© 2003 by the Center For Social Research, Parkland College
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Dongola Chert is recovered from the St. Louis Formation, as is Cobden. The difference between it and Cobden is the brown tones of the matrix.
The texture is fine.
Luster tends to be waxy to glassy.
Against a tan to brown background will be a series of concentric bands of yet darker material.
Fossils are uncommon.
Structural attributes will include: occasional and widely spaced microscopic voids some of which will be lined with iron oxide; the occasional expression of druse; and the occasional oolite.
Dongola Chert is not typically heat treated.
The illustrated specimens were recovered from erosional features in the north half of Section 35, two miles west of the the village of Cobden, Union County, Illinois.
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