sedimentary

Limestone

Sedimentary Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale), Color: tan, buff, or light grey, Luster: dull to earthy, Structure: fine-grained/micritic or bioclast-rich, Cleavage: none (conchoidal to irregular fracture).

Identified July 10, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale), Color: tan, buff, or light grey, Luster: dull to earthy, Structure: fine-grained/micritic or bioclast-rich, Cleavage: none (conchoidal to irregular fracture).

Formation & geological history

Formed in shallow marine environments from the accumulation of shell, coral, algal, and fecal debris, or through chemical precipitation. The provided coordinates (near Luanda, Angola) are consistent with the Cenozoic and Cretaceous sedimentary basins of the West African margin.

Uses & applications

Used extensively in construction (aggregate, cement production), as a building stone (limestone blocks), and in agriculture to neutralize soil acidity.

Geological facts

Limestone makes up about 10% of the Earth's total volume of sedimentary rocks. It often contains fossils and is the primary rock type in karst landscapes where caves form.

Field identification & locations

Identified by its softness (can be scratched by a steel nail) and its fizzing reaction when exposed to dilute hydrochloric acid. It is very common in coastal sedimentary basins of Angola.