sedimentary
Septarian Nodule (Septarian Dragon Stone)
Septarian Concretion (CaCO3 + Al2Si2O5(OH)4)
Hardness: 3.5-4 (Mohs); Color: Brown (siderite/mudstone), yellow (calcite), black (aragonite); Luster: Earthy to waxy; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
- Hardness
- 3
- Luster
- Earthy to waxy
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Physical properties
Hardness: 3.5-4 (Mohs); Color: Brown (siderite/mudstone), yellow (calcite), black (aragonite); Luster: Earthy to waxy; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
Formation & geological history
Formed during the Cretaceous period (approx. 50-70 million years ago). Decomposing sea life killed by volcanic eruptions caused mud balls to form around them, which then shrank, cracked, and were filled by minerals like calcite.
Uses & applications
Primarily used for ornamental purposes, home decor, lapidary arts, jewelry, and as a popular collector's mineral.
Geological facts
The name comes from the Latin word 'septum' meaning partition, referring to the cracks or separations within the rock. They are nicknamed 'Dragon Stones' due to their scaly, cracked appearance resembling dragon skin.
Field identification & locations
Identify by characteristic 'lightning bolt' patterns or internal cavities filled with yellow crystals. Commonly found in Utah (USA), Madagascar, and the UK.
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