sedimentary

Limestone

Sedimentary rock composed mainly of calcite (CaCO3)

Hardness: 3 on the Mohs scale; Color: Typically white, gray, tan, or yellowish; Luster: Dull to earthy; Crystal structure: Microcrystalline or granular; Cleavage: Rhombohedral (in calcite crystals); Specific Gravity: 2.7 - 2.9

Hardness: 3 on the Mohs scale
Color: Typically white, gray, tan, or yellowish
Luster: Dull to earthy

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation of skeletal fragments of marine organisms such as coral, algal, and molluscan remains, typically in shallow marine environments over millions of years.

Uses & applications

Widely used in construction as building material, an aggregate for the base of roads, as an ingredient in making Portland cement, and in agriculture to neutralize acidic soils.

Geological facts

Limestone often contains fossils of ancient marine life. Famous architectural structures like the Great Pyramid of Giza were partially constructed using limestone.

Field identification & locations

Can be easily identified in the field by its characteristic fizz or effervescence when a drop of weak hydrochloric acid is applied to its surface due to the release of carbon dioxide.

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Sandstone or Siltstone

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Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

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Sedimentary Sandstone

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Quartz pebble

Silicon dioxide (SiO2)

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Generic Pebble / Rock Fragment

Lithic fragment / Weathered rock

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Banded Siltstone / Mudstone Pebble

Siltstone / Argillite

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