sedimentary

Limestone Gravel

Sedimentary Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale), Color: tan to light grey, Luster: dull to earthy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None visible in small gravel fragments

Identified July 21, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale), Color: tan to light grey, Luster: dull to earthy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None visible in small gravel fragments

Formation & geological history

Formed by the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. Can also form through the precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Primarily used as construction aggregate, road base, railroad ballast, and in the production of cement and lime.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most limestone is biological in origin and may contain tiny fossils.

Field identification & locations

Identify in the field by its light color, soft nature (can be scratched by a copper coin), and its effervescence (bubbles) when touched with a drop of dilute hydrochloric acid.