sedimentary

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: Light grey to beige; Luster: Dull/Earthy; Structure: Microcrystalline to fine-grained; Cleavage: None/Irregular; Specific Gravity: 2.5-2.7

Hardness: 3-4 (Mohs scale)
Color: Light grey to beige
Luster: Dull/Earthy

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: Light grey to beige; Luster: Dull/Earthy; Structure: Microcrystalline to fine-grained; Cleavage: None/Irregular; Specific Gravity: 2.5-2.7

Formation & geological history

Formed by the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. This specific specimen has been rounded and smoothed by water erosion (fluvial or beach action).

Uses & applications

Used extensively in construction as aggregate, in the manufacture of cement, as a soil conditioner in agriculture, and as a base for road construction.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most limestone is organic in origin, meaning it is made from the remains of once-living organisms.

Field identification & locations

Identified in the field by its softness (can be scratched by a steel nail) and its rapid effervescence (fizzing) when in contact with dilute hydrochloric acid. It is commonly found in riverbeds and coastal regions.