Septarian Nodule

Physical Properties

Hardness: 3.5-4 (Mohs); Color: Brown, tan, and cream; Luster: Dull/earthy exterior, vitreous interior; Structure: Microcrystalline with distinct shrinkage cracks (septaria); Specific Gravity: 2.7-3.4

Formation & Geological History

Formed during the Cretaceous period (approx. 50-70 million years ago) in marine environments. They originate as mud balls that dry out, crack, and are later filled with mineral deposits like calcite.

Uses & Applications

Primarily used as decorative display specimens, paperweights, in lapidary work for cabochons, and occasionally in metaphysical collections.

Geological Facts

The word 'septarian' comes from the Latin 'septum' meaning partition, referring to the cracks that divide the nodule. They are often called 'Dragon Stones' due to their scaly appearance.

Field Identification & Locations

Identify in the field by looking for rounded, heavy nodules with a net-like pattern of cracks on the surface. Commonly found in Utah, USA, and Madagascar. When cracked open, they often reveal beautiful yellow calcite crystals.

Identified on: 4/15/2026

Mode: Standard