Where is Septarian Nodule found?
Septarian Nodule (composed of calcite, aragonite, and chalcedony/quartz)
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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 infillings, often referred to as 'Dragon Stone'.
Utah, USA
The 'Moqui Marbles' or 'Navajo Sandstone Concretions' are a type of iron-rich concretion, but some septarian nodules are also found in the region, particularly in Cretaceous shales.
New Zealand
Known for large, spherical Septarian concretions, often found in marine mudstones.
England (e.g., Kimmeridge Clay)
Septarian nodules are common in various Mesozoic marine sedimentary formations.
Canada (e.g., Alberta)
Found in Cretaceous shales, often associated with hydrocarbon deposits.
Collecting tips
- Look in Sedimentary Outcrops. Septarian nodules are found in sedimentary rock formations, particularly shales, mudstones, and limestones. Look for them in eroded riverbeds, coastal cliffs, and road cuts where these rocks are exposed.
- Identify Spherical or Ovoid Shapes. Septarian nodules typically have a rounded, often spherical or ovoid external shape, distinguishing them from surrounding host rock.
- Look for Cracked Surfaces. Sometimes, the external surface may show faint indications of the internal septarian cracks, or the nodule may be partially broken, revealing the crystalline interior.
- Check for Weight and Density. Concretions are often denser and heavier than the surrounding host rock due to their mineral composition.
- Break Open Suspected Nodules. The definitive identification often requires breaking open a nodule to reveal the characteristic internal septarian cracks filled with contrasting minerals.
Quick Check
- Color:
- Dark exterior, yellow/brown/white interior
- Luster:
- Dull exterior, vitreous/pearly interior
- Streak:
- White (for calcite/aragonite/quartz components)
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