Limestone

Physical Properties

Hardness: 3 on Mohs scale; Color: Grey, tan, or white; Luster: Dull to earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None in rock form; Specific Gravity: 2.5-2.7

Formation & Geological History

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

Uses & Applications

Extensively used in construction as aggregate, cement manufacture, and as a soil conditioner in agriculture. Also used in glass making and chemical industries.

Geological Facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary material found in many of the world's most famous caves and karst landscapes.

Field Identification & Locations

Identify in the field by its softness (can be scratched by a penny) and by its effervescence (bubbles) when a drop of dilute hydrochloric acid or strong vinegar is applied. Commonly found in areas that were once prehistoric seafloors.

Identified on: 4/29/2026

Mode: Standard