Where is Fossiliferous Chert found?
Chert with Crinoid Fossils
Got a photo? Identify rocks instantly with the Rockby app
Open the appFossiliferous 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 Fossiliferous Chert
Midwestern United States
Particularly abundant in Mississippian and Pennsylvanian age strata, such as the Burlington Limestone and Keokuk Limestone formations, which are rich in crinoid fossils and have undergone extensive chertification. States like Missouri, Illinois, Iowa, and Indiana are well-known for crinoidal chert.
United Kingdom
Carboniferous Limestone sequences, especially in areas like the Peak District, can yield fossiliferous chert with crinoid remains.
Various global marine sedimentary basins
Wherever conditions for both crinoid life and subsequent silica diagenesis occurred, fossiliferous chert can be found. This includes many Paleozoic and Mesozoic marine successions worldwide.
Collecting tips
- Look in Limestone/Dolostone Formations. Fossiliferous chert often occurs as nodules, lenses, or beds within carbonate rock units. Examine weathered outcrops of limestone or dolostone for resistant chert masses.
- Identify Crinoid Fragments. Learn to recognize the characteristic circular or star-shaped cross-sections of crinoid stem ossicles. These are often lighter in color than the surrounding chert matrix.
- Check Stream Beds and Gravel Pits. Due to its hardness and resistance to weathering, chert often accumulates in stream beds, river gravels, and glacial till, having been eroded from its original bedrock source.
- Use a Hand Lens. A hand lens (10x magnification) can help in identifying smaller crinoid fragments and confirming the microcrystalline texture of the chert.
Quick Check
- Color:
- Gray, brown, black, or tan with lighter (often white) fossil inclusions.
- Luster:
- Dull to waxy.
- Streak:
- White.
Explore Fossiliferous Chert
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.