sedimentary
Septarian Nodule (Dragon Stone)
Carbonate concretion (Calcite and Aragonite in Limestone/Clay)
Hardness: 3.5-4 (Mohs); Color: Yellow (calcite), Dark Brown (aragonite/limestone); Luster: Vitreous to dull; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
- Hardness
- 3
- Color
- Yellow (calcite), Dark Brown (aragonite/limestone)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 3.5-4 (Mohs); Color: Yellow (calcite), Dark Brown (aragonite/limestone); Luster: Vitreous to dull; Crystal structure: Trigonal/Orthorhombic; Specific Gravity: 2.6-2.8
Formation & geological history
Formed in ancient sea beds (Cretaceous period) when volcanic eruptions killed sea life, which settled and formed mud balls. As the sea receded and mud dried, it cracked and minerals like Calcite seeped into the fissures, crystallizing over millions of years.
Uses & applications
Primarily used for ornamental decor, lapidary carvings (points, spheres, bowls), jewelry, and by collectors for its unique aesthetics.
Geological facts
Often called 'Dragon Stone' because the cracked patterns resemble dragon skin. The yellow centers often fluoresce under UV light. Most high-quality specimens come from Utah, USA, and Madagascar.
Field identification & locations
Identify by the distinct cracked 'honeycomb' or 'turtle shell' pattern with yellow crystalline centers surrounded by brown walls. Found inside limestone concretions in specific sedimentary regions.
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