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A small, round grain consisting of concentric layers of calcium carbonate, silica, or dolomite that have precipitated around a shell fragment, sand grain, pellet of alga, or other central object. Also called ooid.

[oo- (since ooliths resemble fish roe in texture and appearance) + -lith.]

o′o·lith′ic adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Geological Science) any of the tiny spherical grains of sedimentary rock of which oolite is composed
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Siliciclastic material is mostly represented by clay, except in the Aseri Formation, where phosphatic or goethitic ooliths and admixture of quartz sand are recorded.
Both these main tidal channels lead seawards (north-westwards) to a broad shoal area of merged tidal deltas where precipitation of CaC[O.sub.3] from the warm highly saline agitated water leads to the production of ooliths (sand grains with a core surrounded by concentric layers of calcium carbonate).
The iron-ooid interval in Aguilon includes several limestone bands with abundant, small-size, well-sorted ooliths. These layers show a marked lenticular shape and are separated by clear discontinuities (Aurell et al., 1994).