Oolite

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For other uses, see Oolite (disambiguation).

An oolite is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. The name derives from the Greek word oon meaning egg.

Ooids are most commonly composed of calcium carbonate (calcite or aragonite), but can be composed of phosphate, chert, dolomite or iron minerals, including hematite. Dolomitic and chert ooids are most likely the result of the replacement of the original texture in limestone. Oolitic hematite occurs at Red Mountain near Birmingham, Alabama along with oolitic limestone.

Some example Oolitic limestone, a common term for an oolite, was formed in the United Kingdom during the Jurassic period, and forms the Cotswold Hills, the Isle of Portland, and part of the North Yorkshire Moors. A particular type, Bath Stone, gives the buildings of the World Heritage City of Bath, England their distinctive appearance.

This type of limestone is also found in Indiana, USA. The town of Oolitic, Indiana was founded for the trade of limestone and bears its name. Quarries in Bedford, Oolitic, and Bloomington, Indiana contributed the materials for such iconic United States landmarks as the Empire State Building and the Pentagon. The Soldiers' and Sailors' Monument (Indianapolis) in downtown Indianapolis is built almost solely of grey oolitic limestone.

The famous movie Breaking Away centers around the sons of quarry workers in Bloomington, Indiana, the home of Indiana University. Almost all of Indiana University is built with native oolitic limestone material.