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Banded Missouri Chert - My Sedimentary Rock

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From Jones1rocks

Banded Missouri Chert - My Sedimentary Rock

Banded Chert with Calcite and Pyrite

Where This Rock Is From (place, type of locality, etc.)

Osage Beach, Missouri: Road Cut

What This Rock Is

Banded tan and white chert with calcite and pyrite. Roubidoux Formation, early Ordovician (chert only).

What I Like About This Rock

New roads were being cut to alleviate traffic congestion in the Lake of the Ozarks area in Missouri. On a weekend visit, and on a spur of the moment idea, we decided to look at the rock up close. The cherts were amazing, and had outstanding tan, black, and gray banding, many with quart druse on their surface. This specimen was plucked (not chiseled) out of a small pocket.

Advice

  • Investigated geologic maps to determine the formation. Be very careful of traffic and falling rock at roadcuts. Photograph was taken on my kitchen table, on my navy blue shirt, with indirect lighting from a halogen worklight, and directed lighting from a LED flashlight illuminating the shirt in back.

Andrew Alden, Geology Guide, says:

Fresh roadcuts are always worth investigating for specimens like this. Within a year, those pyrite crystals deteriorate and stain the rocks with brown streaks. Thanks, too, for the photography notes. It's a real challenge to capture the visual interest that rocks present to the unaided eye.

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