Where is Chert found?
Chert (a microcrystalline variety of quartz)
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Open the appChert occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Chert
North America
Widespread in the Appalachian Mountains, Ozark Mountains (e.g., Burlington Chert), and throughout the midwestern and western United States. Significant flint deposits in Ohio, Indiana, and Texas.
Europe
Abundant in chalk formations of England (e.g., Dover Cliffs), France, and other parts of Western Europe. Also found in sedimentary sequences across the continent.
Asia
Occurs in various sedimentary basins, particularly in regions with extensive limestone and shale deposits. Notable occurrences in parts of China, India, and the Middle East.
Australia
Found in sedimentary successions, often associated with ancient marine environments.
Collecting tips
- Look in Carbonate Rocks. Chert nodules and beds are frequently found interbedded with or replacing limestone and dolomite. Examine road cuts, quarries, and stream beds in areas with exposed carbonate stratigraphy.
- Identify Conchoidal Fracture. A key diagnostic feature is its characteristic conchoidal (shell-like) fracture, which produces sharp, curved edges. This is often visible on broken surfaces.
- Check Hardness. Chert is hard (Mohs 7) and will scratch glass and steel. This helps distinguish it from softer sedimentary rocks.
- Observe Color and Luster. While variable, the waxy to dull luster and often muted colors are characteristic. Flint, a common variety, is typically dark gray to black.
- Examine for Fossils. Biogenic chert may contain microscopic or macroscopic fossils of siliceous organisms, or even silicified remains of other organisms.
Quick Check
- Color:
- Variable (white, gray, black, brown, red, green)
- Luster:
- Waxy to dull, sometimes vitreous
- Streak:
- White
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