sedimentary

Limestone Pebble

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: tan to light grey; Luster: dull/earthy; Texture: fine-grained and rounded; Cleavage: none; Specific Gravity: 2.3-2.7

Hardness: 3 on Mohs scale
Color: tan to light grey
Luster: dull/earthy

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: tan to light grey; Luster: dull/earthy; Texture: fine-grained and rounded; Cleavage: none; Specific Gravity: 2.3-2.7

Formation & geological history

Formed in shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. It can also form through chemical precipitation from ocean or lake water.

Uses & applications

Used largely in road construction, as a concrete aggregate, and in the production of lime and cement. Small pebbles are often used in landscaping.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is highly susceptible to acid rain, which can cause it to dissolve over time.

Field identification & locations

Can be identified in the field by its softness (scratched by steel) and a bubbling reaction when exposed to a weak acid like vinegar. Found globally in ancient seabed deposits.