sedimentary

Limestone Cobble

Sedimentary Limestone (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs); Color: Grayish-white to tan; Luster: Dull/Earthy; Structure: Fine-grained/Microcrystalline; Cleavage: None; Specific Gravity: 2.5-2.7

Hardness: 3-4 (Mohs)
Color: Grayish-white to tan
Luster: Dull/Earthy

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs); Color: Grayish-white to tan; Luster: Dull/Earthy; Structure: Fine-grained/Microcrystalline; Cleavage: None; Specific Gravity: 2.5-2.7

Formation & geological history

Formed from the accumulation of calcium carbonate and marine organism remains (shells, coral) in shallow marine environments. This specimen shows significant rounding from water erosion (fluvial or glacial activity).

Uses & applications

Raw material for cement, lime and mortar production. Also used as crushed aggregate for road construction and as a soil conditioner (agricultural lime).

Geological facts

Limestone is very susceptible to acid; it will fizz when touched with vinegar. It often contains micro-fossils not visible to the naked eye.

Field identification & locations

Identify by its reaction to dilute hydrochloric acid or vinegar. This rounded shape indicates it was tumbled in a river or creek bed over a long period. Found globally in areas that were once prehistoric sea beds.