sedimentary

Concretionary Sandstone

Clastic Sedimentary Rock (Sandstone with secondary mineral cementation)

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs/quartz grains); Color: Tan, buff, or light brown; Luster: Dull or earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Hardness: 6-7 (Mohs/quartz grains)
Color: Tan, buff, or light brown
Luster: Dull or earthy

Identified June 5, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs/quartz grains); Color: Tan, buff, or light brown; Luster: Dull or earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Formation & geological history

Formed by the precipitation of mineral cement (such as silica, calcium carbonate, or iron oxides) in the spaces between sediment grains. These often form around a nucleus in marine or terrestrial sedimentary basins, often dating from the Paleozoic to Mesozoic eras.

Uses & applications

Limited industrial use; primarily used as a landscape rock, architectural stone, or as a curiosity/collectible specimen due to its unique knobby shapes.

Geological facts

Concretions are often mistaken for fossils or dinosaur eggs because of their unusual, organic-looking shapes. The ‘Moqui Marbles’ of Utah are a famous small-scale example of iron-oxide concretions.

Field identification & locations

Identify by its bumpy, nodular texture which is harder than the surrounding host rock. Commonly found in eroded canyons, riverbeds, and sedimentary outcrops worldwide. Collectors look for symmetrical or highly unusual 'sculptural' forms.