sedimentary

Limestone (Buff/Tan)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3-4 (Mohs scale); Color: buff, tan, or light brown; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Rhombohedral; Specific Gravity: 2.3–2.7

Hardness: 3-4 (Mohs scale)
Color: buff, tan, or light brown
Luster: dull to earthy

Identified February 22, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Mohs scale); Color: buff, tan, or light brown; Luster: dull to earthy; Crystal Structure: Trigonal (as calcite); Cleavage: Rhombohedral; Specific Gravity: 2.3–2.7

Formation & geological history

Formed primarily from the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. It can also be formed by the chemical precipitation of calcium carbonate from lake or ocean water.

Uses & applications

Extensively used in construction as aggregate, for making cement, as a decorative building stone, and in the production of lime. It is also used as a soil conditioner in agriculture.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of carbon for carbon capture technology and frequently contains well-preserved fossils.

Field identification & locations

Identified in the field by its reaction to dilute hydrochloric acid (it fizzes). Look for massive, bedded structures in quarry exposures or natural outcrops in karst landscapes.