Where is Septarian Nodule found?
Septarian Nodule (composed of calcite, aragonite, and chalcedony/quartz within a host rock like shale or mudstone)
Got a photo? Identify rocks instantly with the Rockby app
Open the appSeptarian Nodule 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 Septarian Nodule
Madagascar
Known for large, well-formed Septarian nodules with prominent yellow calcite and dark brown host rock, often from Cretaceous deposits.
Utah, USA
Specifically the Morrison Formation, yielding nodules with distinct patterns and often containing aragonite and calcite.
New Zealand
Found in various sedimentary formations, often with a dark gray matrix and light-colored infillings.
England
Occurrences in Jurassic and Cretaceous sedimentary rocks, particularly along coastlines.
Collecting tips
- Look in Sedimentary Outcrops. Search in areas with exposed shale, mudstone, or marl beds, especially those that show signs of weathering and erosion, which can expose concretions.
- Coastal and Riverine Environments. Erosion by water can free nodules from their host rock, making them discoverable on beaches, riverbeds, and stream banks.
- Examine Weathered Surfaces. Septarian nodules are often harder than their host rock and may weather out as distinct, rounded masses. Look for spherical or ovoid shapes protruding from rock faces.
- Check for Cracks and Infillings. Once a nodule is found, look for the characteristic internal cracks filled with contrasting minerals. A fresh break or cut will reveal the septarian structure.
Quick Check
- Color:
- Dark gray/brown exterior, yellow/white/clear interior cracks.
- Luster:
- Dull to earthy exterior, vitreous to waxy interior.
- Streak:
- White (for calcite/aragonite/quartz), variable for host rock (often gray to brown).
Explore Septarian Nodule
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.