sedimentary
Septarian Nodule (Dragon Stone)
Septarian concretion (Complex of Calcite, Aragonite, and Limestone/Clay)
Hardness: 3.5-4 (Mohs); Color: Brown, yellow, cream, and grey; Luster: Waxy to dull (matrix), vitreous to pearly (crystals); Crystal system: Trigonal (calcite/aragonite); Cleavage: Perfect rhombohedral in crystals.
- Hardness
- 3
- Color
- Brown, yellow, cream, and grey
- Luster
- Waxy to dull (matrix), vitreous to pearly (crystals)
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3.5-4 (Mohs); Color: Brown, yellow, cream, and grey; Luster: Waxy to dull (matrix), vitreous to pearly (crystals); Crystal system: Trigonal (calcite/aragonite); Cleavage: Perfect rhombohedral in crystals.
Formation & geological history
Formed as concretions in sedimentary seafloors approximately 50 to 70 million years ago (Cretaceous period). Dehydration of clay cores caused shrinkage cracks (septaria) which were later filled by calcite and aragonite precipitation.
Uses & applications
Primarily used as decorative lapidary items, spheres, bookends, and jewelry. It is highly valued in the 'metaphysical' and rock collecting communities for its unique 'dragon-skin' appearance.
Geological facts
The name comes from the Latin word 'septum', meaning partition, referring to the cracks that divide the specimen. While the outer shell is often hard limestone, the inner cavities (vugs) are frequently lined with sparkling yellow calcite crystals.
Field identification & locations
Identify by its unique angular 'cracked' patterns (septaria) filled with yellow or translucent minerals. Common locations include Utah (USA), Madagascar, and the United Kingdom. Look for large, heavy rounded nodules in shale or mudstone deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary