sedimentary

Limestone

Calcium Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: White, tan, or light gray; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (calcite); Specific gravity: 2.3-2.7

Hardness: 3 (Mohs scale)
Color: White, tan, or light gray
Luster: Dull to earthy

Identified June 1, 2026More sedimentary →

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Physical properties

Hardness: 3 (Mohs scale); Color: White, tan, or light gray; Luster: Dull to earthy; Crystal structure: Trigonal/Hexagonal (calcite); Specific gravity: 2.3-2.7

Formation & geological history

Formed in marine environments through the accumulation of shell, coral, and algal debris or by precipitation from water. Most specimens date from the Paleozoic to Cenozoic eras.

Uses & applications

Used widely in construction as aggregate, in cement manufacturing, as a soil conditioner in agriculture, and as a flux in steel making.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary mineral that forms massive cave systems and karst topography.

Field identification & locations

Identify in the field by its softness (can be scratched by a penny) and its strong reaction (effervescence) when exposed to a drop of weak acid such as vinegar.