sedimentary

Oolitic Limestone

Oosparite / Oolitic Calcarenite (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale), Color: Cream, tan, grey, and white; Luster: Dull to pearly; Crystal structure: Hexagonal/trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.

Hardness: 3 (Mohs scale), Color: Cream, tan, grey, and white
Color: Cream, tan, grey, and white
Luster: Dull to pearly

Identified July 18, 2026More sedimentary →

Explore Oolitic Limestone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3 (Mohs scale), Color: Cream, tan, grey, and white; Luster: Dull to pearly; Crystal structure: Hexagonal/trigonal (as calcite); Cleavage: Perfect rhombohedral; Specific gravity: 2.7.

Formation & geological history

Formed in warm, shallow, supersaturated marine environments where calcium carbonate precipitates around a nucleus (like a sand grain or shell fragment) in agitated waters, creating spherical grains called ooids. Most originate from the Jurassic or Carboniferous periods.

Uses & applications

Used as building stone, aggregate for roads, flux in steel making, agricultural lime, and in decorative jewelry or polished palm stones due to its unique texture.

Geological facts

The word 'ooid' is derived from the Greek word for egg, because the small grains resemble fish eggs. These stones are a primary component of many famous monuments, including several buildings in Washington, D.C.

Field identification & locations

Identify by looking for concentrations of small, round, egg-like spheres (ooids) embedded in a matrix. It will react and fizz strongly when exposed to dilute hydrochloric acid. Commonly found in limestone quarries in the UK (Portland Stone) and the US (Indiana Limestone).