sedimentary

Limestone (River Pebble)

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale); Color: light gray to off-white; Luster: dull/earthy; Texture: fine-grained and smooth due to water erosion; Cleavage: none; Specific gravity: 2.5-2.7

Hardness: 3 (Mohs scale)
Color: light gray to off-white
Luster: dull/earthy

Identified April 21, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: light gray to off-white; Luster: dull/earthy; Texture: fine-grained and smooth due to water erosion; Cleavage: none; Specific gravity: 2.5-2.7

Formation & geological history

Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen has been further shaped by river or coastal erosion (abraded into a smooth pebble).

Uses & applications

Used in construction (aggregate), cement manufacturing, soil conditioning (lime), and as a common decorative garden stone.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of carbon for the global cycle and often contains micro-fossils not visible to the naked eye.

Field identification & locations

Identify in the field by its softness (can be scratched by a steel nail) and its reaction to dilute hydrochloric acid (it will fizz/effervesce). Look for it in riverbeds or coastal areas.