Where is Fossiliferous Chert found?
Chert (a variety of microcrystalline quartz) with fossil inclusions
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
North America
Widespread in the Appalachian Mountains (e.g., Onondaga Chert, New York), Ozark Mountains (e.g., Burlington Chert, Missouri), and throughout the midwestern and western United States in various Paleozoic and Mesozoic formations. Notable for silicified corals, brachiopods, and crinoids.
Europe
Common in chalk formations (e.g., Cretaceous chalks of England and France, containing flint nodules with sponge spicules and microfossils). Also found in various Paleozoic and Mesozoic marine sequences across the continent.
Australia
Occurs in various sedimentary basins, including the Pilbara Craton (Precambrian stromatolitic cherts) and other regions with marine sedimentary rocks.
Asia
Found in numerous locations, particularly in regions with extensive marine sedimentary deposits, such as China, India, and Russia, often containing radiolarian cherts or silicified macrofossils.
Collecting tips
- Look in Sedimentary Outcrops. Chert with fossils is commonly found in areas with exposed sedimentary rock layers, particularly those rich in limestone, shale, or ancient marine deposits. Riverbeds and road cuts can expose these layers.
- Identify Chert Characteristics. First, identify the chert matrix by its hardness (scratches glass), conchoidal fracture, and waxy to dull luster. Then, look for embedded structures that appear organic in origin.
- Examine for Fossil Textures. Fossils may appear as distinct shapes, textures, or color variations within the chert. Use a hand lens to examine surfaces for fine details of shells, skeletal fragments, or plant matter.
- Check for Silicified Remains. Many fossils in chert are silicified, meaning their original material has been replaced by silica. These can be very well-preserved and stand out against the chert matrix.
- Safety Precautions. When collecting, wear appropriate safety gear, including gloves and eye protection, especially if breaking rocks. Be aware of sharp edges produced by conchoidal fracture. Chert is primarily silicon dioxide (SiO2), and prolonged inhalation of fine dust generated during cutting or grinding can lead to silicosis, a serious lung disease. Always work in well-ventilated areas or use respiratory protection (e.g., N95 mask) when generating dust.
Quick Check
- Color:
- Variable (white, gray, black, brown, red, green, yellow)
- Luster:
- Dull to waxy, vitreous on fresh fracture
- Streak:
- White
Explore Fossiliferous Chert
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.