sedimentary

Limestone

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness 3 on Mohs scale; color ranges from light grey, beige, tan to white; dull to earthy luster; microcrystalline or massive structure; reacts (effervesces) strongly with diluted hydrochloric acid.

Identified July 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily in shallow, warm marine environments through the accumulation and compaction of organic debris like shells, coral, and algal remains, or chemical precipitation of calcium carbonate over millions of years.

Uses & applications

Widely used in construction as building stone, crushed stone for aggregate, component in cement and lime production, soil conditioner in agriculture, and neutralizer in chemical processes.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. Over time, heat and pressure can metamorphose limestone into marble.

Field identification & locations

Identified by its relatively soft surface (scratchable with a steel nail) and positive reaction to acid tests. Commonly found in ancient sea beds, karst topography regions, and exposed cliff faces worldwide.