Definitions for "Ooid"
A type of sedimentary grain found in limestones. It has the appearance of small (generally 1-2mm) grains with concentric internal structure, formed by thin algal films formed as currents roll the grain back and forth.
Tiny round grains composed of concentric layers around a nucleus, usually calcium carbonate.
A small, rounded, light-colored concretion which forms as the mineral aragonite builds up successive layers around a nucleus such as a mineral grain or brine shrimp fecal pellet