Where is Banded Chert found?
Chert (variety Flint/Jasper)
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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
Extensive chert deposits are found in the Appalachian Mountains (e.g., Devonian Oriskany Sandstone, Mississippian Fort Payne Chert), the Ozark Plateau, and various locations in California (e.g., Franciscan Complex radiolarian cherts).
United Kingdom
Flint (a variety of chert) is abundant in the Cretaceous Chalk formations, particularly in southern England (e.g., Sussex, Kent).
Australia
Significant banded chert occurrences, including jasper, are found in Western Australia (e.g., Hamersley Basin banded iron formations, Pilbara Craton).
Canada
Chert is common in various sedimentary basins, including the Arctic Archipelago and parts of Ontario and Quebec.
South Africa
Ancient banded chert formations are part of the Barberton Greenstone Belt, dating back to the Archean Eon.
Collecting tips
- Look in Sedimentary Sequences. Chert often occurs as nodules or beds within limestone, chalk, or shale formations. Examine road cuts, stream beds, and quarries in areas known for these rock types.
- Check for Conchoidal Fracture. A key identifier for chert is its characteristic conchoidal (shell-like) fracture, which produces sharp edges. This is often visible on broken surfaces.
- Observe Banding. For banded chert, look for distinct, parallel layers of varying colors or textures. This banding can be subtle or very pronounced.
- Hardness Test. Chert is very hard (Mohs 7). It will scratch glass and steel. Carry a steel file or a piece of quartz for comparison.
- Examine Weathered Surfaces. Chert is highly resistant to weathering, often standing out as resistant layers or nodules in softer host rocks. Weathered surfaces may have a duller appearance but the banding might still be visible.
Quick Check
- Color:
- Varied, often banded (white, gray, black, red, brown, yellow, green)
- Luster:
- Dull to waxy, sometimes vitreous on fresh breaks
- Streak:
- White
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