sedimentary
Septarian Nodule
Calcite-bearing Septarian Concretion
Hardness: 3.5 - 4 (Mohs); Color: Grey, brown, and yellow; Luster: Waxy to dull; Crystal structure: Trigonal (calcite centers); Specific Gravity: 2.7
- Hardness
- 3
- Color
- Grey, brown, and yellow
- Luster
- Waxy to dull
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Physical properties
Hardness: 3.5 - 4 (Mohs); Color: Grey, brown, and yellow; Luster: Waxy to dull; Crystal structure: Trigonal (calcite centers); Specific Gravity: 2.7
Formation & geological history
Formed during the Cretaceous period (50-70 million years ago) in marine environments where mud and organic matter aggregated and contracted, creating cracks later filled by calcite.
Uses & applications
Ornamental displays, lapidary work, jewelry making, and metaphysical collecting.
Geological facts
Also known as 'Dragon Stones' because of their fractured, scaly appearance that resembles dragon skin; the name comes from the Latin 'septum', meaning partition.
Field identification & locations
Look for rounded, clay-heavy nodules in sedimentary basins; when cracked open, they reveal distinctive angular cavities filled with yellow calcite and brown aragonite.
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