sedimentary
Septarian Nodule
Septarian Concretion (CaCO3 / Fe2O3 / SiO2)
Hardness: 3.5-4 (Mohs scale); Color: Yellow (calcite), brown (aragonite), grey (limestone); Luster: Waxy to vitreous; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
- Hardness
- 3
- Color
- Yellow (calcite), brown (aragonite), grey (limestone)
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 3.5-4 (Mohs scale); Color: Yellow (calcite), brown (aragonite), grey (limestone); Luster: Waxy to vitreous; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
Formation & geological history
Formed as concretions in sea beds during the Cretaceous period (approx. 50-70 million years ago). Internal cracks formed as they dried and were later filled with minerals like calcite and aragonite.
Uses & applications
Primarily used as decorative display pieces, spheres, bookends, and in jewelry (cabochons). Highly valued by metaphysical collectors.
Geological facts
The word comes from the Latin 'septum' (partition) or 'septem' (seven), referring to the crack patterns. Famous locations include Utah, USA, and Madagascar.
Field identification & locations
Identified by a characteristic 'dragon skin' or cracked appearance with distinct color zones of yellow, brown, and grey. Found in shale or clay deposits.
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