sedimentary

Oolitic Limestone (Oolite)

Oolitic Limestone (primarily Calcium Carbonate, CaCO3)

Hardness: 3-4 (Mohs scale); Color: Light brown, tan, or creamy grey; Luster: Dull to earthy; Structure: Composed of tiny spherical grains called ooids (<2mm diameter); Cleavage: None (conchoidal fracture likely).

Hardness: 3-4 (Mohs scale)
Color: Light brown, tan, or creamy grey
Luster: Dull to earthy

Identified March 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in warm, shallow, oversaturated marine waters. Ooids form as concentric layers of calcium carbonate precipitate around a nucleus (like a sand grain) in agitated water. Most common in Jurrasic or Carboniferous aged strata.

Uses & applications

Used as a decorative building stone (Portland stone), in road construction, as a source of lime for agriculture, and as a flux in steel making.

Geological facts

The word 'oolite' comes from the Greek word 'oon' for egg, because the stone looks like fish roe. Much of the iconic architecture in Bath and London, UK, is built from oolitic limestone.

Field identification & locations

Identify by looking for the 'fish egg' texture and applying a drop of vinegar; it will effervesce (fizzle) due to the calcium carbonate content. Commonly found in coastal or formerly marine regions of the USA, UK, and the Bahamas.

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