sedimentary
Oolitic Limestone
Oosparite / Oolitic Calcarenite (CaCO3)
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
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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).
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