sedimentary
Chert nodules
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs), Color: White to grey with tan rinds, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
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Physical properties
Hardness: 7 (Mohs), Color: White to grey with tan rinds, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6
Formation & geological history
Formed by the precipitation of silica within sedimentary layers, often limestone or dolomite. Large deposits in this Missouri region (Ozarks) date to the Mississippian and Ordovician periods.
Uses & applications
Historically used for stone tools (knapping). Currently used for gravel, road construction, and as a common find for mineral collectors.
Geological facts
In Missouri, chert is commonly known as 'flint' and is extremely abundant in the Ozark Plateau. It is often found as nodules or layered beds resistant to weathering.
Field identification & locations
Identify by its conchoidal (shell-like) fracture pattern and its ability to scratch glass. Found commonly in creek beds and road cuts across the Missouri Ozarks.
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Clastic Sedimentary Rock Grain (SiO2 dominated)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Shale or Slaty Mudstone
Argillaceous sedimentary rock
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Sandstone
Arenite (primarily SiO2)
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