Where is Chert found?
Chert
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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, and throughout the midwestern and western United States in various Paleozoic and Mesozoic formations. Notable occurrences include the Burlington Limestone (Midwest), Fort Payne Chert (southeastern US), and Arkansas Novaculite.
Europe
Abundant in chalk formations (e.g., Cretaceous Chalk of England and France, where it is known as flint), and in various Paleozoic and Mesozoic sedimentary sequences across the continent.
Asia
Found in numerous sedimentary basins, particularly in association with ancient marine deposits and ophiolite complexes (e.g., radiolarian cherts).
Australia
Occurs in various sedimentary successions, including Precambrian banded iron formations and younger marine deposits.
Collecting tips
- Look for Nodules and Beds. Chert often forms as distinct nodules or concretions within softer host rocks like limestone or dolomite. Look for these hard, rounded to irregular masses. It can also occur as continuous beds.
- Check for Conchoidal Fracture. A key identifying feature is its conchoidal (shell-like) fracture, which produces sharp, curved edges. This is often visible on broken surfaces.
- Test Hardness. Chert is very hard (Mohs 7) and will scratch glass and steel. This distinguishes it from softer sedimentary rocks.
- Observe Luster. The luster is typically dull to waxy, which can help differentiate it from more vitreous quartz crystals.
- Examine Associated Rocks. Chert is frequently found in close association with carbonate rocks (limestone, dolomite) and sometimes shales. Understanding the local geology can guide your search.
Quick Check
- Color:
- Variable (white, gray, black, brown, red, green)
- Luster:
- Dull to waxy
- Streak:
- White
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