sedimentary

River Stone (Limestone)

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale), Color: tan to creamy beige, Luster: dull to waxy when wet, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture possible)

Identified July 4, 2026More sedimentary →

Explore River Stone (Limestone) 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: tan to creamy beige, Luster: dull to waxy when wet, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture possible)

Formation & geological history

Formed by the accumulation of shells, coral, algal, and fecal debris in clear, warm, shallow marine waters. This specific specimen has been rounded and smoothed by water erosion in a river environment.

Uses & applications

Commonly used as decorative garden stones, in construction aggregate, as a source for lime in cement, and occasionally for lapidary tumbling for beginners.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Because it is composed of calcium carbonate, it will fizz if a drop of weak acid (like vinegar) is applied to it.

Field identification & locations

Identify in the field by its soft texture, reactivity to acid, and presence in riverbeds. It is found globally in areas that were once prehistoric seafloors.