Where is Banded Chert found?
Sedimentary Chert
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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 Ouachita Mountains (Arkansas and Oklahoma, including Novaculite), the Appalachian Mountains, and the Great Lakes region (e.g., Burlington Chert in Illinois, Bayport Chert in Michigan).
United Kingdom
Flint (a variety of chert) is common in the Chalk Group formations across southern England, particularly along the coastlines (e.g., Dover cliffs).
Australia
Significant occurrences of banded chert, including jasper, are found in Western Australia, often associated with Precambrian Banded Iron Formations.
Canada
Chert is found in various sedimentary sequences across Canada, including the Rocky Mountains and the Canadian Shield.
Japan
Radiolarian cherts are common in accretionary complexes throughout Japan, reflecting deep-sea deposition.
Collecting tips
- Look for Hardness. Chert is very hard (Mohs 7). It will scratch glass and steel. This is a key diagnostic property.
- Observe Fracture. Look for a characteristic conchoidal (shell-like) fracture, which produces sharp, curved edges. This is a hallmark of cryptocrystalline silica.
- Examine Banding. For banded chert, observe the distinct, parallel layers of varying color or texture. This is the primary identifying feature for this specific variety.
- Check for Associated Rocks. Chert often occurs as nodules or beds within limestone or dolomite, or as bedded deposits in deep-marine sedimentary sequences, sometimes associated with shales or volcanic rocks.
- Consider Color and Luster. While variable, the dull to waxy luster and wide range of colors (often earthy tones) can help narrow down identification.
Quick Check
- Color:
- Variable, often banded (white, grey, black, brown, red, green, yellow)
- Luster:
- Dull to waxy, sometimes vitreous on fresh fracture
- Streak:
- White
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