sedimentary
Septarian Nodule (Polished)
Septarian concretion (Calcite, Aragonite, Limestone)
Hardness 3-4 (Calcite/Aragonite), tan to brown with distinct veining, often white or yellow calcite and brown aragonite, dull to vitreous luster depending on polish.
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 3-4 (Calcite/Aragonite), tan to brown with distinct veining, often white or yellow calcite and brown aragonite, dull to vitreous luster depending on polish.
Formation & geological history
Formed in marine environments during the Cretaceous period (50-70 million years ago) through the accumulation of organic matter and subsequent diagenetic processes leading to concretion and cracking, filled visually by mineral rich groundwater.
Uses & applications
Popular in lapidary, carved into shapes like hearts, spheres, and bookends for decorative purposes and collecting.
Geological facts
Septarian nodules are also known as 'Dragon Stones' due to their cracked, scaly appearance. The name comes from the Latin word 'septum' meaning partition.
Field identification & locations
Recongnized by the contrasting colors of the host rock (often grey or tan mudstone/limestone) and the distinct crystalline veins (yellow/white calcite, brown aragonite). Usually found in areas that were ancient sea beds.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary