sedimentary
Septarian Nodule (Dragon Stone)
Calcite-Aragonite-Limestone Septarian
Hardness: 3.5-4 (Mohs); Color: Yellow (calcite), brown (aragonite), grey (limestone); Luster: Vitreous to dull; Crystal structure: Trigonal/Orthorhombic; Specific gravity: 2.7-2.9
- Hardness
- 3
- Color
- Yellow (calcite), brown (aragonite), grey (limestone)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 3.5-4 (Mohs); Color: Yellow (calcite), brown (aragonite), grey (limestone); Luster: Vitreous to dull; Crystal structure: Trigonal/Orthorhombic; Specific gravity: 2.7-2.9
Formation & geological history
Formed during the Cretaceous period (50-70 million years ago) when volcanic eruptions killed sea life that sank to the ocean floor. Decomposing matter attracted minerals that formed nodules; as the seabed dried and cracked, calcite and aragonite filled the cavities.
Uses & applications
Primarily used as decorative display specimens, for jewelry (mostly cabochons), and highly valued by metaphysical practitioners and rock collectors.
Geological facts
Septarian is often called 'Dragon Stone' because the internal pattern resembles dragon skin or scales. They are unique among concretions because of their distinctive shrinking cracks (septaria) filled with mineral precipitates.
Field identification & locations
Identify by its 'angular' look with distinct color zoning between the yellow center and brown borders. Found mostly in Utah (USA) and Madagascar.
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