sedimentary

Limestone Pebble

Limestone (CaCO3)

Hardness: 3 (Mohs scale), Color: light grey to beige, Luster: dull to earthy, Texture: fine-grained, smooth from water erosion. Reacts with dilute hydrochloric acid.

Identified July 19, 2026More sedimentary →

Explore Limestone Pebble in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3 (Mohs scale), Color: light grey to beige, Luster: dull to earthy, Texture: fine-grained, smooth from water erosion. Reacts with dilute hydrochloric acid.

Formation & geological history

Formed in shallow marine environments from the accumulation of calcium carbonate, including shell fragments and coral. This specific shape is the result of mechanical weathering and transport in water.

Uses & applications

Limestone is majorly used in the production of cement, as a flux in steel making, and as a soil conditioner in agriculture. Small river pebbles are used in landscaping and aquariums.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type in which most caves and karst topography develop due to its solubility in rainwater.

Field identification & locations

Identify by its relatively soft surface (can be scratched by a copper coin/steel) and its bubbling reaction to acid. Commonly found in riverbeds, lakeshores, and ancient sea beds.