sedimentary
Septarian Nodule (Dragon Stone)
Septarian Concretion (CaCO3 + MgCO3 + Clay)
Hardness: 3.5-4; Color: Grey (clay), Yellow (calcite), Brown (siderite/aragonite); Luster: Earthy to vitreous; Structure: Trigonal/Orthorhombic in cracks.
- Hardness
- 3
- Color
- Grey (clay), Yellow (calcite), Brown (siderite/aragonite)
- Luster
- Earthy to vitreous
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Physical properties
Hardness: 3.5-4; Color: Grey (clay), Yellow (calcite), Brown (siderite/aragonite); Luster: Earthy to vitreous; Structure: Trigonal/Orthorhombic in cracks.
Formation & geological history
Formed roughly 50 to 70 million years ago during the Cretaceous period. Shrinkage cracks in dehydrating clay nodules were later filled with minerals like calcite and aragonite.
Uses & applications
Mainly used for decorative ornamental pieces, jewelry (cabochons), mineral collecting, and metaphysical purposes.
Geological facts
The name comes from the Latin word 'septum' meaning partition/seven, referring to the cracks that divide the nodule. They are often called 'Dragon Stones' due to their scaly appearance.
Field identification & locations
Identify by a grey mudstone exterior with distinct yellow/brown crystalline patterns inside. Commonly found in Utah, USA and Madagascar.
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