Where is Septarian Nodule found?
Septarian Nodule (composed of calcite, aragonite, and often limestone or mudstone)
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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 producing large, high-quality Septarian nodules with excellent contrast between the dark matrix and bright yellow calcite.
Utah, USA
The 'Dragon Egg' Septarian nodules from the Morrison Formation are famous for their distinctive patterns and often contain brown aragonite and yellow calcite.
New Zealand
Found in various sedimentary deposits, often with well-defined septaria.
England (e.g., Kimmeridge Clay)
Septarian nodules are found in Jurassic marine shales, often containing pyrite.
Collecting tips
- Look in Sedimentary Formations. Focus your search on areas with exposed marine shales, mudstones, and limestones, particularly those from Mesozoic or Cenozoic eras. Riverbeds and coastal exposures can also reveal eroded nodules.
- Identify Nodule Shapes. Septarian nodules are typically spherical, ovoid, or irregularly rounded. Look for these shapes weathering out of softer host rock.
- Check for Internal Cracks. If a nodule is broken, look for the characteristic internal network of mineral-filled cracks. Unbroken nodules may show subtle external indications of internal structure.
- Be Prepared for Hard Digging. While some nodules weather out easily, others may be embedded in harder rock and require tools for extraction. Always obtain permission before collecting on private or protected lands.
Quick Check
- Color:
- Dark gray/brown exterior, yellow/brown/white interior veins.
- Luster:
- Dull exterior, vitreous to pearly interior.
- Streak:
- White (for calcite/aragonite), gray/brown (for mudstone/limestone matrix).
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