sedimentary
Sandstone Concretion
Clastic sedimentary rock (primarily Quartz SiO2)
Hardness: 6-7 (Mohs scale); Color: tan, buff, or light brown; Luster: dull/earthy; Texture: granular, sandy feel; Crystal structure: none (clastic); Cleavage: none.
- Hardness
- 6-7 (Mohs scale)
- Color
- tan, buff, or light brown
- Luster
- dull/earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs scale); Color: tan, buff, or light brown; Luster: dull/earthy; Texture: granular, sandy feel; Crystal structure: none (clastic); Cleavage: none.
Formation & geological history
Formed by the precipitation of mineral cement (like calcite or silica) within the spaces between sand grains. This often happens around a nucleus, such as a fossil or organic matter, during the diagenesis process in sedimentary basins over millions of years.
Uses & applications
Commonly collected as curiosities due to their strange shapes. Sandstone generally is used in construction and paving, though concretions specifically are used for landscaping or as decorative objects.
Geological facts
Concretions are often mistaken for fossils, eggs, or man-made tools due to their unusual and sometimes ergonomic shapes. Some giant concretions, like the Moeraki Boulders in New Zealand, can grow to several meters in diameter.
Field identification & locations
Identify by the sandy texture and often rounded or bulbous shapes that stand out from the surrounding flatter layers of rock. Found in sandstone outcrops, riverbeds, and desert regions where erosion exposes them.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
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
Sandstone
Arenite
sedimentary