sedimentary

Septarian Nodule

Septarian Concretion (CaCO3 with Siderite/Calcite)

AI-generated identification · may be incorrect

Hardness: 3.5-4 (Mohs); Color: Brown, tan, and gray with yellow/white veins; Luster: Dull to earthy (matrix), Vitreous (veins); Structure: Concretions with dehydration cracks.

Hardness: 3
Color: Brown, tan, and gray with yellow/white veins
Luster: Dull to earthy (matrix), Vitreous (veins)

Identified May 26, 2026More sedimentary →

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Physical properties

Hardness: 3.5-4 (Mohs); Color: Brown, tan, and gray with yellow/white veins; Luster: Dull to earthy (matrix), Vitreous (veins); Structure: Concretions with dehydration cracks.

Formation & geological history

Formed during the Cretaceous period (approx. 50-70 million years ago) in marine environments. Clay balls shrank and cracked through dehydration, and minerals like calcite precipitated into the cracks.

Uses & applications

Used primarily for ornamental items, interior design, jewelry (cabochons), and as museum-quality display specimens for collectors.

Geological facts

The name 'Septarian' comes from the Latin word 'septum', meaning partition, referring to the cracks that divide the concretion into distinct sections. They are often called 'Dragon Stones'.

Field identification & locations

Identified by distinct 'turtle-back' patterns of cracks on the surface or internal chambers filled with crystals. Commonly found in Utah, USA, and Madagascar.