Limestone

Physical Properties

Hardness: 3-4 on Mohs scale; Color: Cream, light gray, or tan; Luster: Dull to earthy; Texture: Fine-grained to clastic; Cleavage: None (conchoidal fracture possible); Specific Gravity: 2.5–2.7.

Formation & Geological History

Formed primarily from the accumulation of shell, coral, algal and fecal debris in marine environments. It can also form through chemical precipitation from lake or ocean water. Most deposits are millions of years old, dating from various geologic eras.

Uses & Applications

Extensively used in construction (as aggregate or building stone), cement manufacturing, soil conditioning in agriculture, and as a precursor for lime (calcium oxide).

Geological Facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock type found in karst landscapes, resulting in massive cave systems like Mammoth Cave in Kentucky.

Field Identification & Locations

Identify in the field by applying a small amount of diluted hydrochloric acid; it will effervesce (fizz) vigorously. It is commonly found in ancient seabed regions, cliffs, and quarries.

Identified on: 4/24/2026

Mode: Standard