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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