sedimentary

Limestone (River Pebble)

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: light gray to white; Luster: matte/dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: Perfect rhombohedral in crystal form, but none visible in pebble; Specific Gravity: 2.7

Hardness: 3 on Mohs scale
Color: light gray to white
Luster: matte/dull

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen has been weather-worn into a smooth pebble by fluvial or coastal transport.

Uses & applications

Primarily used as a building material, aggregate for concrete, manufacture of cement, and as a soil conditioner in agriculture.

Geological facts

Approximately 10% of all sedimentary rocks are limestones. They often contain fossils of ancient marine life and are essential for the formation of cave systems through chemical weathering.

Field identification & locations

Identify by its light color and softness; it can be scratched by a steel copper penny or knife. It reacts and fizzes when in contact with weak acid (like vinegar). Commonly found in riverbeds and coastal regions.

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