sedimentary
Concretion
Septarian Concretion (Fragmentary)
Hardness: 3-4 (if carbonate-based); Color: Tan, beige, or grey; Luster: Dull/Earthy; Structure: Hard, compact mass with distinctive parallel ridging or 'bands'; Composition: Siderite, Calcite, or Fine-grained Sandstone.
- Hardness
- 3-4 (if carbonate-based)
- Color
- Tan, beige, or grey
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-4 (if carbonate-based); Color: Tan, beige, or grey; Luster: Dull/Earthy; Structure: Hard, compact mass with distinctive parallel ridging or 'bands'; Composition: Siderite, Calcite, or Fine-grained Sandstone.
Formation & geological history
Formed through the precipitation of mineral cement in the spaces between particles in a sediment layer, often around a nucleus like a leaf or shell. This specimen displays weathering patterns that reveal internal structural layers.
Uses & applications
Primarily for geological study, decorative display, and specimen collecting.
Geological facts
Concretions are often mistaken for fossils (like dinosaur eggs or vertebrae) due to their organized, organic-looking shapes. They can grow to be several meters in diameter, such as the Moeraki Boulders.
Field identification & locations
Identify by looking for a shape that contrasts with the surrounding bedding planes and distinctive internal layering. Common in shale and sandstone deposits worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary