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Common as Dirt

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Published on: Feb. 2, 1998

Last revision: Oct. 28, 2010

weathering changes the rock's appearance and tooling qualities. The chert rocks strewn over the ground and piled along streams are inferior for tools. Prehistoric Missourians dug open mines to secure the best chert for making tools. They also traded for special quality stone and stone tools, sometimes over long distances.

Today we find chert flakes in plowed fields that used to be Indian campsites. The abundant flakes are the non-biodegradable litter of thousands of years of tool makers. Occasionally, we may find pieces of the tools themselves and, more rarely, a perfect blade or point, hundreds or thousands of years old. Chert was also important for its ability to produce sparks which could start fires and later, to ignite gunpowder in flint-lock firearms.

In Missouri, chert usually appears in small fragments or narrow bands embedded in limestone and dolomite, or as loose rocks in the soil or along streams. But chert also can be found in sedimentary formations tens to hundreds of feet thick. These solid chert formations resulted from long accumulation of tiny marine animals and sponges that secrete glasslike particles of silica. A good example of this is the almost continuous layers of dense chert within the dolomite bluffs along some Ozark streams.

Some of these "chert reefs" are so persistant over wide areas that geologists use them as reference layers or "marker beds" to help them map the geological layers above and below the reefs. Primitive animals that once lived in these reefs sometimes show up in the rock as chert fossils, preserving the form of the once-living organisms. Even thicker beds of chert form the novaculite deposits in Arkansas' Ouachita Mountains. This special chert is mined to produce the famous "Arkansas stone" whetstones, which sharpen tools all over the world.

Missouri's most impressive beds of thick, solid chert are in the exposed cliffs and glades near Joplin and along Shoal Creek in Jasper and Newton counties. These unusual features are easy to see in Joplin's Wildcat Park and adjoining Wildcat Glade Natural Area on the city's southwest side. Wildcat Glade sports an interesting assemblage of plants-a mosaic of lichen-covered rock, patches of gnarled, stunted oaks and showy wildflowers, such as coreopsis, glade onion, rock pink, prickly pear and Barbara's buttons.

Grand Falls on Shoal Creek is only minutes from Wildcat Park and is perhaps Missouri's most scenic chert feature. Here, Shoal Creek plunges 15 feet over a ledge of solid chert to continue southward. In addition to its novel bedrock and great beauty, Grand Falls holds the Missouri record as our highest, continuously flowing falls. (Missouri has many higher waterfalls, but they don't flow all year.)

So keep an eye out for chert-that common old rock that played a role in human culture and contributes much to Missouri's natural character.

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