sedimentary

River Stone (Limestone)

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: tan, grey, beige; Luster: dull to earthy; Texture: smooth, water-worn; Cleavage: none visible in pebble form; Specific gravity: 2.3-2.7

Hardness: 3-4 (Mohs scale)
Color: tan, grey, beige
Luster: dull to earthy

Identified July 17, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: tan, grey, beige; Luster: dull to earthy; Texture: smooth, water-worn; Cleavage: none visible in pebble form; Specific gravity: 2.3-2.7

Formation & geological history

Formed through the accumulation of organic debris such as shells or chemical precipitation in marine environments. This specimen was subsequently smoothed and rounded by the abrasive action of water (river or beach) over many years.

Uses & applications

Commonly used as decorative landscaping stones, aquarium substrate, or as a natural 'worry stone' for tactile comfort. Industrial limestone is used in cement production.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Many river stones like this one contain microscopic fragments of ancient marine life.

Field identification & locations

Identified by its rounded shapes, matte finish, and reaction to acids (bubbles with vinegar). Found worldwide in riverbeds, beaches, and glacial deposits.