Where is Chert with Quartz found?
SiO2 (Chert) with SiO2 (Quartz)
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Open the appChert with Quartz 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 with Quartz
North America
Extensive chert deposits are found in the midwestern and eastern United States (e.g., Burlington Chert, Fort Payne Chert), often associated with Mississippian and Ordovician limestones. Flint Ridge in Ohio is famous for its colorful chert. Quartz veins and geodes are common throughout the Appalachian Mountains and other orogenic belts.
Europe
Flint (a variety of chert) is abundant in the chalk formations of England (e.g., Dover Cliffs) and France. Significant chert occurrences are also found in the Mediterranean region and Eastern Europe. Quartz is ubiquitous in many European mountain ranges and sedimentary basins.
Australia
Chert is found in various sedimentary basins, including the Pilbara Craton (Precambrian cherts) and in association with banded iron formations. Quartz is widespread across the continent.
Asia
Chert deposits are common in many parts of Asia, particularly in association with ancient marine sediments and ophiolite complexes. Quartz is found in numerous localities, including significant deposits in China and India.
Collecting tips
- Look in Sedimentary Rocks. Chert is most commonly found as nodules or layers within limestone, dolomite, and shale formations. Look for areas where these rocks are exposed, such as road cuts, stream beds, and quarries.
- Identify Conchoidal Fracture. A key characteristic of chert is its conchoidal fracture. If you find a hard, fine-grained rock that breaks with smooth, curved surfaces resembling broken glass, it's likely chert. Quartz crystals will also exhibit this fracture if not breaking along crystal faces.
- Check for Hardness. Both chert and quartz are very hard (Mohs 7). They will scratch steel and glass. This helps differentiate them from softer sedimentary rocks.
- Observe Luster. Chert often has a dull to waxy luster, while macroscopic quartz crystals will have a distinct vitreous (glassy) luster. The contrast can help identify areas where quartz has grown within chert.
- Look for Geodes and Veins. Quartz crystals often form in geodes (hollow, crystal-lined cavities) or veins within chert or surrounding host rocks. Look for rounded or irregular masses that might contain crystalline interiors.
Quick Check
- Color:
- Variable (gray, white, black, brown, red, green for chert; colorless, white, milky for quartz, but can be varied)
- Luster:
- Dull to waxy (chert), Vitreous (quartz)
- Streak:
- White
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