What's the noun for oolite? Here's the word you're looking for.
oolith
(geology) A spherical granule of which oolite is composed, formed by concentric accretion of thin layers of a mineral around a core. Calcium carbonate (limestone) is the most common mineral that forms ooliths, but they may also form from other minerals such as dolomite and silica.
“Siliciclastic material is mostly represented by clay, except in the Aseri Formation, where phosphatic or goethitic ooliths and admixture of quartz sand are recorded.”