sedimentary

Septarian Nodule

Septarian Concretion (CaCO3 with Siderite/Limonite streaks)

AI-generated identification · may be incorrect

Hardness: 3.5-4 (Mohs); Color: Tan, brown, white, and yellow; Luster: Dull to waxy; Structure: Microcrystalline with irregular veins; Cleavage: None (conchoidal fracture).

Hardness: 3
Color: Tan, brown, white, and yellow
Luster: Dull to waxy

Identified May 18, 2026More sedimentary →

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Physical properties

Hardness: 3.5-4 (Mohs); Color: Tan, brown, white, and yellow; Luster: Dull to waxy; Structure: Microcrystalline with irregular veins; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed during the Cretaceous period (50-70 million years ago) from mud balls and organic matter in ancient seabeds that cracked and were filled with minerals like calcite.

Uses & applications

Primarily used for lapidary work, decorative display pieces, jewelry (cabochons), and collection specimens. Often sliced and polished to show internal 'dragon skin' patterns.

Geological facts

Also known as 'Dragon Stones' due to their scaly appearance. They are unique because they form from the inside out as the core shrinks and cracks.

Field identification & locations

Found in dry lake beds or riverbanks, especially in Utah and Madagascar. Identify by the 'septaria' (cracks) that reveal contrasting mineral fillers against the base rock.