sedimentary
Septarian Nodule
Septarian Concretion (CaCO3-rich mudstone with Calcite/Aragonite veins)
Hardness: 3.5 to 4.0; Color: Brown, tan, and yellow; Luster: Waxy to dull; Structure: Massive concretion with internal shrinkage cracks filled with crystals; Specific Gravity: 2.7.
- Hardness
- 3
- Color
- Brown, tan, and yellow
- Luster
- Waxy to dull
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Physical properties
Hardness: 3.5 to 4.0; Color: Brown, tan, and yellow; Luster: Waxy to dull; Structure: Massive concretion with internal shrinkage cracks filled with crystals; Specific Gravity: 2.7.
Formation & geological history
Formed during the Cretaceous Period (50-70 million years ago) from sediment at the bottom of ancient seas. As the mud dried and shrunk, cracks formed (septaria) and were later filled with minerals like calcite or aragonite.
Uses & applications
Primarily used as decorative display pieces, in jewelry making (cabochons), and as spiritual or geological collectibles.
Geological facts
The name comes from the Latin 'septum' meaning partition, referring to the cracks. They are often nicknamed 'Dragon Stones' due to their scaly appearance.
Field identification & locations
Identify by looking for 'honeycomb' or 'turtle shell' patterns on the surface. Commonly found in Utah (USA) and Madagascar. To identify in the field, look for round or egg-shaped stones with visible veins.
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