Where is Septarian Nodule found?
Septarian Nodule (calcite-filled concretions)
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
Utah, USA
The most famous locality for high-quality Septarian nodules, particularly from the Cretaceous period, known for large, well-formed specimens with vibrant yellow calcite.
Madagascar
Produces large, often beautifully polished Septarian nodules with distinct patterns and sometimes a mix of calcite and aragonite.
New Zealand
Known for Septarian concretions, often referred to as 'Moeraki Boulders' (though these are technically concretions, not always septarian in the classic sense, but share similar formation processes and appearance).
England (e.g., Kimmeridge Clay)
Smaller Septarian nodules can be found in Jurassic and Cretaceous marine shales.
Canada (e.g., Alberta)
Occurrences in Cretaceous sedimentary formations.
Collecting tips
- Look in Sedimentary Outcrops. Septarian nodules are found in sedimentary rock formations, especially shales, mudstones, and marls. Look for eroded areas, riverbeds, or coastal cliffs where these rocks are exposed.
- Identify Concretionary Shapes. Search for spherical to ovoid, often lumpy or potato-shaped rocks that stand out from the surrounding matrix due to their harder composition.
- Check for Broken Specimens. Sometimes, eroded nodules will be broken open, revealing the characteristic internal calcite veins, which is a definitive identifier.
- Acid Test (Caution). A small drop of dilute hydrochloric acid (HCl) will effervesce on the calcite veins, confirming their presence. Always use caution and appropriate safety gear when handling acids.
Quick Check
- Color:
- Dull brown/gray exterior, yellow/white/orange calcite veins internally.
- Luster:
- Earthy exterior, vitreous to pearly interior (calcite).
- Streak:
- White (for calcite component).
Explore Septarian Nodule
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.