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Andrew Alden

Mississippi Chert

By July 17, 2013

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mississippi chertA mystified reader from Mississippi sent this photo of a large streambed boulder; he'd never seen anything like it. Very few Mississippians have, because such a thing is found only in the farthest northeastern corner of the state. It's Devonian chert, a rarity in this state of much younger mudstones.

Your own neighborhood may be nothing but chert; it's certainly common where I live. But it's always good to be reminded that everything in the world is marvelous to somebody. And I ended up discovering an excellent booklet, "Windows into Mississippi's Geologic Past," published by the state geological agency.

More:
Mississippi geology
Geologic map of Mississippi
About chert
Photo courtesy Doug Kilgore

Comments

July 19, 2013 at 9:09 am
(1) dave says:

this link does not seem to work: “Windows into Mississippi’s Geologic Past,” at least on my computer it doesn’t.

July 19, 2013 at 1:51 pm
(2) Geology Guide says:

I’ve replaced the link; try it now.

July 22, 2013 at 7:42 am
(3) glen says:

do you have a link to a much larger picture of the chert? I live in neighboring Louisiana and grew up in an area of the Catahoula Formation in northwest Catahoula Parish. We have several rocky creekbeds in which I’ve found very unusual chalcedony formations, drusy quartz, ancient marine invertebrate fossils, fossilized wood, orthoclase stones tumbled smooth and round, and even unakite cobbles! I’d love to compare what is pictured to some of the stuff I find.

July 22, 2013 at 2:14 pm
(4) Geology Guide says:

The full-size photo is blurry enough that it really doesn’t show more than the thumbnail does.

The Catahoula area is at the mouth of the Ouachita River, which drains the mountains of Arkansas and brings down the various interesting rocks you mention. The Mississippi location is on the opposite side of the Miss. River and its rocks may not correspond to yours. But white translucent chert or quartzite looks the same everywhere; it’s kind of an anonymous rock.

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