sedimentary

Septarian Nodule

Calcite-bearing Septarian Concretion

AI-generated identification · may be incorrect

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

Identified June 26, 2026More sedimentary →

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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.