sedimentary

Limestone Pebble

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Tan to light brown; Luster: Dull/earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.3-2.7

Hardness: 3 on Mohs scale
Color: Tan to light brown
Luster: Dull/earthy

Identified March 5, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Tan to light brown; Luster: Dull/earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.3-2.7

Formation & geological history

Formed by the accumulation of shell, coral, algal, and fecal debris in marine environments. Often dates from the Paleozoic or Mesozoic eras. This specimen shows signs of mechanical weathering and rounding by water transport.

Uses & applications

Used primarily in construction (crushed stone, cement), agriculture (soil conditioner), and as a chemical feedstock. Small pebbles such as this have low commercial value but are useful for educational purposes.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Many limestones contain visible fossils of marine organisms like crinoids or brachiopods.

Field identification & locations

Identify in the field by its softness (can be scratched by a steel nail) and its effervescence when exposed to a weak acid like vinegar. Common in riverbeds and ancient seafloors.