ovoid(redirected from ovoids)
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(1) A large spherical phenocryst in magmatic rock resulting from the partial resorption of a previously formed phenocryst. Ovoids are a characteristic feature of the rapakivi granite in the vicinity of Vyborg.
(2) A spherical limestone grain having a radial structure. Certain varieties of ovoids are oolites. Ovoids form oolitic and ovoid limestones.