Cobden Chert
© 2003 by the Center For Social Research, Parkland College
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Cobden Chert is recovered from the St. Louis Formation, as is Dongola. The difference between it and Dongola is the brown tones of Dongola's matrix.
TEXTURE:
The texture is fine.
LUSTER:
Luster tends to be glassy.
COLOR:
Against a dark gray to blue-black background will be a series of concentric bands of yet darker material.
FOSSILS:
Fossils are uncommon.
STRUCTURAL CHARACTERISTICS:
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.
HEAT TREATMENT:
Cobden Chert is not typically heat treated.
SOURCE:
The illustrated specimen was recovered from an erosional feature in the north half of Section 35, two miles west of the the village of Cobden, Union County, Illinois.
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