Where is Chert found?
Chert (microcrystalline 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 Plateau, and throughout the midwestern and western United States in various Paleozoic and Mesozoic sedimentary formations. Notable occurrences include the Burlington Limestone (Midwest), Fort Payne Chert (Appalachians), and Arkansas Novaculite (Ouachita Mountains).
Europe
Common in chalk formations (e.g., Cretaceous Chalk of England and France, where it is known as flint), and in various Mesozoic and Cenozoic sedimentary basins.
Asia
Found in numerous sedimentary sequences, particularly in deep-sea chert formations associated with ophiolites and accretionary prisms (e.g., Japan, Himalayas).
Australia
Occurs in various sedimentary basins, including Precambrian banded iron formations and younger marine sequences.
Collecting tips
- Look in Carbonate Terrains. Chert nodules are frequently found weathering out of limestone and dolomite bedrock, often accumulating in residual soils and stream beds in such areas.
- Examine Road Cuts and Quarries. These exposures often reveal chert layers or nodules within sedimentary rock sequences.
- Check Stream Beds and Gravel Pits. Due to its hardness and resistance to weathering, chert is a common component of river gravels and alluvial deposits.
- Identify Conchoidal Fracture. A key diagnostic feature is the smooth, curved, shell-like fracture surface, often with sharp edges.
- Test Hardness. Chert is hard (Mohs 7) and will scratch glass and steel.
Quick Check
- Color:
- Variable (gray, brown, black, white, red)
- Luster:
- Dull to waxy
- Streak:
- White
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