sedimentary

Septarian Nodule Slice

Calcite-bearing Septarian Concretion

Hardness: 3.5-4 (Calcite veins) to 6-7 (Chert/Shale matrix). Color: Dark brown or grey matrix with cream/yellow veins. Luster: Dull/earthy matrix with vitreous veins. Crystal Structure: Hexagonal (calcite) and amorphous. cleavage: Rhombohedral in veins.

Hardness: 3
Color: Dark brown or grey matrix with cream/yellow veins
Luster: Dull/earthy matrix with vitreous veins

Identified July 11, 2026More sedimentary →

Explore Septarian Nodule Slice in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed during the Cretaceous period (approx. 50-70 million years ago) in marine environments. They began as mud balls that cracked as they dried and contracted, which were later filled with minerals like calcite.

Uses & applications

Primarily used as decorative specimens, bookends, lapidary slices, and used in jewelry or as meditation stones in the metaphysical community.

Geological facts

The name 'Septarian' comes from the Latin word 'septum', meaning partition or wall, referring to the characteristic cracks that divide the concretion into distinct sections.

Field identification & locations

Identified by the distinct 'spider web' or angular vein patterns. They are commonly found in Utah, USA and Madagascar. Look for rounded nodules in shale deposits; internal patterns are only visible when cut or cracked open.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Mudstone

Argillite / Siliciclastic sedimentary rock

sedimentary

Brown Sandstone (River Rock)

Arenite

sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary