A pisolite () is a sedimentary rock made of pisoids, which are concretionary grains – typically of calcium carbonate which resemble ooids, but are more than 2 mm in diameter.Mindat - Pisolite These grains are approximately spherical and have concentric layers reaching 10 mm in diameter.
Bauxites, limonites, and siderites often have a pisolitic structure.
See also Ooid Oolite
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