Septarian Nodule (Dragon Stone)

Physical Properties

Hardness: 3.5-4 (Mohs); Color: Brown, yellow, grey, and black; Luster: Vitreous to dull; Crystal structure: Trigonal (calcite) / Orthorhombic (aragonite); Cleavage: Perfect rhombohedral in centers.

Formation & Geological History

Formed during the Cretaceous period (50-70 million years ago) when volcanic eruptions killed marine life, which sank to the sea floor. Mud balls formed around shells, dried, cracked, and were later filled with calcite and aragonite deposits.

Uses & Applications

Primarily used as decorative display specimens, lapidary carvings (points/spheres), jewelry, and metaphysical 'healing' stones.

Geological Facts

Also known as 'Dragon Stones' due to their cracked, scaly appearance. The name comes from the Latin word 'septum', meaning partition, referring to the cracks that divide the concretion.

Field Identification & Locations

Identify by the unique 'angular' cracking pattern (septaria) filled with yellow calcite and brown aragonite. Commonly found in Utah (USA) and Madagascar.

Identified on: 4/16/2026

Mode: Standard