sedimentary

Oolitic Limestone

Oolitic Carbonate (CaCO3)

Hardness: 3 (Mohs scale); Color: Cream, tan, yellowish, or light brown; Luster: Pearly to earthy; Structure: Composed of tiny spherical grains called ooids (0.25 to 2 mm in diameter) with concentric layers; Cleavage: None (fractures across grains).

Hardness: 3 (Mohs scale)
Color: Cream, tan, yellowish, or light brown
Luster: Pearly to earthy

Identified March 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in warm, shallow, supersaturated marine environments where calcium carbonate precipitates around a nucleus (like a shell fragment or sand grain). Agitated by wave action, these grains grow into concentric spheres and eventually cement together. Typically found in strata ranging from Jurassic to modern day.

Uses & applications

Used widely in construction as a building stone (e.g., Indiana Limestone), in the manufacture of lime and cement, for soil conditioning in agriculture, and occasionally as a decorative stone in landscaping.

Geological facts

Famous structures like the Empire State Building and the Pentagon are constructed primarily from oolitic limestone. The term 'oolite' comes from the Greek word 'oon' for egg, because the rock resembles fish roe.

Field identification & locations

Identify in the field by the distinct 'fish egg' texture of the ooids and its reaction (effervescence) when a small drop of dilute hydrochloric acid is applied. Commonly found in locations like the Cotswolds (UK), Indiana (USA), and the Bahamas.