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Oolites, Pisolites and Laterites Formation and Composition

Oolites

Composition:

Oolite is a sedimentary rock made up of ooids (ooliths) that are cemented together. Most oolites are limestones — ooids are made of calcium carbonate (minerals aragonite or calcite).

Description:

Ooids are spheroidal grains with a nucleus and mineral cortex accreted around it which increases in sphericity with distance from the nucleus. Nucleus is usually either mineral grain or biogenic fragment. The term “ooid” is applied to grains less than 2 mm in diameter. Larger grains with similar genesis are pisoids (pisoliths). Rocks made up of pisoids is pisolite.

Formation and Environment:

Ooids usually possess a clearly developed growth banding. Ooids may be spherical but some are elongated, depending on the shape of nucleus. Most ooids are marine, forming in shallow (less than 10 m, preferably even less than 2 meters), warm, and wave-agitated water such as the Persian Gulf and the Bahama Platform.

Oolites, Pisolites and Laterites Formation and Composition

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