sedimentary

Sandstone Concretion

Sandstone (Sedimentary Rock) with silica or calcite cement

AI-generated identification · may be incorrect

Hardness: 6-7 (if silica) or 3 (if calcite). Color: Tan, beige, or brown with visible wood-like grain. Luster: Dull/Earthy. Structure: Clastic/Spherical. Specific gravity: 2.3-2.6.

Hardness: 6-7 (if silica) or 3 (if calcite)
Color: Tan, beige, or brown with visible wood-like grain
Luster: Dull/Earthy

Identified April 28, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (if silica) or 3 (if calcite). Color: Tan, beige, or brown with visible wood-like grain. Luster: Dull/Earthy. Structure: Clastic/Spherical. Specific gravity: 2.3-2.6.

Formation & geological history

Formed by the precipitation of mineral cement within the spaces between sediment grains. These often form around a nucleus (like a leaf or shell) and grow outward in round shapes within sedimentary layers.

Uses & applications

Mostly used as curiosity pieces or garden decor. In some historical contexts, smooth round concretions were used as game stones or projectiles.

Geological facts

They are often mistaken for fossilized eggs or cannonballs due to their remarkably spherical shape. Some very large ones, like the Moeraki Boulders in New Zealand, can be several meters wide.