Limestone

Physical Properties

Hardness: 3 (Mohs scale); Color: light gray, tan, or white; Luster: earthy to dull; Crystal structure: Trigonal (microcrystalline); Specific gravity: 2.3–2.7

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 ocean or lake water.

Uses & Applications

Used widely in construction (aggregate, cement), agriculture (neutralizing soil acidity), and as a precursor for chemical industries. Fine varieties are used in sculpture.

Geological Facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the world's caves are formed in limestone because it is soluble in slightly acidic groundwater.

Field Identification & Locations

Identify in the field by its light color and characteristic effervescence (bubbling) when a drop of weak hydrochloric acid or vinegar is applied. Commonly found in former marine basins.

Identified on: 4/14/2026

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