sedimentary

Sandstone Concretion with Quartz Center

Sedimentary Clastic Rock (SiO2 matrix with Quartz core)

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale); Color: Earthy brown to gray exterior with white/translucent crystalline center; Luster: Dull/earthy (exterior), Vitreous (internal crystals); Structure: Clastic grain texture with a secondary mineral inclusion; Specific Gravity: 2.6-2.7.

Hardness: 6-7 (Mohs scale)
Luster: Dull/earthy (exterior), Vitreous (internal crystals)

Identified March 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of sand-sized mineral particles or rock fragments. The distinct center likely formed through 'concretion' or 'vug-filling,' where mineral-rich water deposited quartz or calcite in a void within the sandstone layers during diagenesis.

Uses & applications

Common sandstone is used in construction and paving. Specimens with aesthetic inclusions are kept by amateur collectors for study and display.

Geological facts

Sandstone preserves a record of ancient environments like deserts or riverbeds. The white 'patch' in this specimen indicates a localized mineral concentration where the rock was more porous or had a hollow cavity during its formation history.

Field identification & locations

Identify in the field by its gritty texture (feels like sandpaper) and visible layering or inclusions. Often found in riverbeds, cliffs, and sedimentary basins. Collectors look for unique color patterns or 'eyes' like the one seen here.