Where is Banded Chert found?
Chert (variety Jasper/Agate)
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Open the appBanded Chert 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 Banded Chert
United States
Oregon (Picture Jasper), California (various jaspers), Idaho, Wyoming, Arizona, Michigan (Petoskey Stone - fossilized coral replaced by chert), Ohio (Flint Ridge).
Brazil
Known for large deposits of agate, often with vibrant banding.
India
Significant source of various jaspers and agates.
Madagascar
Produces a wide range of colorful jaspers and agates.
Australia
Known for Mookaite Jasper and other banded cherts.
Russia
Ural Mountains are a source of various ornamental jaspers.
Collecting tips
- Look in Sedimentary Formations. Search in areas with exposed sedimentary rocks, especially those that were once marine environments. Chert often occurs as nodules within limestone or chalk, or as bedded layers within shale or siltstone.
- Check Riverbeds and Gravel Pits. Erosion can transport chert nodules and fragments into river systems. Look for smooth, dense, often colorful pebbles and cobbles with conchoidal fractures.
- Examine Road Cuts and Construction Sites. Freshly exposed rock faces can reveal chert layers or nodules that are otherwise hidden.
- Identify Conchoidal Fracture. A key identifier for chert is its characteristic conchoidal (shell-like) fracture, which produces sharp edges. This is often visible on broken pieces.
- Test Hardness. Chert is hard (Mohs 6.5-7). It will scratch glass and steel. This helps distinguish it from softer rocks.
Quick Check
- Color:
- Banded, highly variable (red, brown, yellow, gray, white, blue, green, black)
- Luster:
- Waxy to dull
- Streak:
- White
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