sedimentary

Limestone (Crushed Gravel)

Limestone (Calcium Carbonate, CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale. Color: Light grey, white, buff, to brownish. Luster: Dull to earthy. Crystal structure: Trigonal (microcrystalline calcite). Cleavage: Perfect rhombohedral in calcite crystals, though blocky to irregular in massive limestone.

Hardness: 3 on Mohs scale
Color: Light grey, white, buff, to brownish
Luster: Dull to earthy

Identified July 25, 2026More sedimentary →

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Physical properties

Formation & geological history

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

Uses & applications

Extensively used as crushed stone for road base, gravel driveways, construction aggregate, concrete production, soil acidity neutralizer in agriculture, and manufacturing of cement and lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Famous geological features like karst landscapes, sinkholes, and massive cave systems (including stalactites and stalagmites) form primarily in limestone formations.

Field identification & locations

Easily identified by its light grey color, soft scratch test (can be scratched by a steel nail), and strong effervescence (fizzing) when exposed to dilute hydrochloric acid or vinegar. Extremely common worldwide.