sedimentary

Limestone (River Pebble / Fossiliferous Limestone)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Grayish-tan, off-white, light brown; Luster: Dull, earthy; Texture: Fine-grained with small fossil fragments or vugs; Specific Gravity: ~2.5-2.7.

Hardness: 3 on Mohs scale
Color: Grayish-tan, off-white, light brown
Luster: Dull, earthy

Identified July 26, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Grayish-tan, off-white, light brown; Luster: Dull, earthy; Texture: Fine-grained with small fossil fragments or vugs; Specific Gravity: ~2.5-2.7.

Formation & geological history

Formed through the accumulation and compaction of organic debris such as shell fragments, coral, and calcium carbonate precipitates in shallow marine environments over millions of years, followed by river or beach water erosion that rounded the pebble.

Uses & applications

Used in construction, cement manufacturing, soil conditioning, crushed stone aggregate, and as decorative river rocks or garden landscaping elements.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth and frequently contains well-preserved microfossils or shell imprints.

Field identification & locations

Identified by its soft hardness (scratched easily with a steel nail) and visible effervescence (fizzing reaction) when exposed to dilute hydrochloric acid. Commonly found along riverbeds, beaches, and sedimentary basins worldwide.