sedimentary
Septarian Nodule (Septarian Dragon Stone)
Septarian Concretion (Composition: Calcite, Aragonite, and Limestone/Clay)
Hardness: 3.5 to 4.0; Color: yellow center (calcite), brown lines (aragonite), and grey exterior (limestone); Luster: Vitreous to dull; Crystal Structure: Trigonal/Orthorhombic mix inside sedimentary matrices; Specific Gravity: 2.6 - 2.8.
- Hardness
- 3
- Luster
- Vitreous to dull
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Physical properties
Hardness: 3.5 to 4.0; Color: yellow center (calcite), brown lines (aragonite), and grey exterior (limestone); Luster: Vitreous to dull; Crystal Structure: Trigonal/Orthorhombic mix inside sedimentary matrices; Specific Gravity: 2.6 - 2.8.
Formation & geological history
Formed during the Cretaceous period (50-70 million years ago) specifically in ancient sea beds. Volcanic eruptions killed sea life which sank to the bottom; as they decomposed, minerals were attracted to the organic matter, forming nodules. As the oceans receded, the nodules dried and cracked, allowing calcite and aragonite to seep in and crystallize.
Uses & applications
Primarily used for ornamental purposes including spheres, bookends, and jewelry (cabochons). It is highly prized by mineral collectors and the metaphysical community as 'Dragon Stone'.
Geological facts
The name comes from the Latin word 'septum', meaning partition, referring to the cracks and separations that divide the nodules. Each specimen is unique because the shrinkage cracks (septaria) form random, distinct patterns.
Field identification & locations
Identify by its distinctive 'cracked' appearance with yellow crystalline centers surrounded by brown walls. Found commonly in Utah, USA, and Madagascar. In the field, look for round, lumpy grey mudstone balls that, when cracked open, reveal yellow crystalline interiors.
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