sedimentary

Limestone (Beach Pebble)

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: White to light grey; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.7.

Hardness: 3-4 (Mohs)
Color: White to light grey
Luster: Dull or earthy

Identified June 26, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs); Color: White to light grey; Luster: Dull or earthy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.7.

Formation & geological history

Formed through the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. This specific specimen has been rounded and smoothed by water erosion/wave action.

Uses & applications

Primary source of lime for cement, used in construction as aggregate, and in the production of glass and steel. As a pebble, it is used in landscaping and aquariums.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It often contains fossils that are too small to see without a microscope.

Field identification & locations

Identify in the field by its white/grey color and soft texture compared to quartz; it will react (fizz) when exposed to a weak acid like vinegar. Commonly found on beaches near chalk or limestone cliffs.