Where is Chert found?
Sedimentary rock (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 central and eastern United States (e.g., Burlington Chert, Fort Payne Chert, Flint Ridge Flint), often associated with Mississippian and Ordovician limestones. Also found in Canada.
Europe
Abundant in the Chalk Group of England (e.g., Dover Cliffs flint), France, and other parts of Western Europe. Also found in various Paleozoic and Mesozoic sedimentary basins.
Asia
Occurs in numerous sedimentary sequences across Asia, including radiolarian cherts in orogenic belts (e.g., Japan, Himalayas) and nodular cherts in carbonate platforms.
Australia
Found in various sedimentary formations, including Precambrian banded iron formations and younger marine sequences.
Collecting tips
- Look in Carbonate Rocks. Chert frequently forms as nodules or layers within limestone and dolomite. Examine outcrops of these rocks for hard, dense, often darker inclusions.
- Check for Conchoidal Fracture. A key diagnostic feature is its characteristic conchoidal (shell-like) fracture. If you break a piece, it will show smooth, curved surfaces similar to broken glass.
- Hardness Test. Chert is harder than steel (Mohs hardness of 7). It will scratch glass and most metals. This distinguishes it from softer sedimentary rocks.
- Examine Weathered Surfaces. Chert is more resistant to weathering than many surrounding rocks. It often stands out in relief on weathered outcrops or forms resistant pebbles and cobbles in stream beds.
- Consider Color and Luster. While variable, chert often has a dull to waxy luster and can be found in a wide range of colors. Flint, a common variety, is typically dark gray to black.
Quick Check
- Color:
- Variable (white, gray, black, brown, red, green, yellow)
- Luster:
- Dull to waxy, sometimes vitreous
- Streak:
- White
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