sedimentary

Sandstone Concretion

Carbonate-cemented Sandstone Concretion

AI-generated identification · may be incorrect

Hardness: 6-7 (approximate), Color: Tan to reddish-brown, Luster: Dull/Earthy, Crystal Structure: Granular/Amorphous, Texture: Coarse sand-like exterior, Shape: Spherical to sub-spherical

Identified July 17, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (approximate), Color: Tan to reddish-brown, Luster: Dull/Earthy, Crystal Structure: Granular/Amorphous, Texture: Coarse sand-like exterior, Shape: Spherical to sub-spherical

Formation & geological history

Formed by the precipitation of mineral cement within the spaces between sediment grains, often around a nucleus like a leaf, shell, or bone. These typically form in sedimentary basins over millions of years as groundwater mineralizes.

Uses & applications

Primarily used as geological curiosities, educational specimens, or garden ornaments. Some large ones are tourist attractions.

Geological facts

Often mistaken for dinosaur eggs or cannonballs due to their near-perfect spherical shape. The 'Moqui Marbles' in Utah are a famous variety of small iron oxide concretions.

Field identification & locations

Identify by looking for spherical shapes that differ in hardness and color from the surrounding host rock. They are commonly found in eroding sandstone bluffs or riverbeds.