Oolites are carbonate sedimentary rocks composed of ooids that are cemented by lime mud. Ooids are smooth, spherical grains, characteristically <2 mm in diameter, that form and grow with the accretion of calcite, aragonite, and micrite around small mineral grains or skeletal fragments as it rolls along a shallow seafloor. This creates an internal concentric layering around a nucleus, indicated by the red and blue markers in the cross-sectional image, which also shows the unweathered micrite matrix, coating and enclosing the ooids allowing for lithification. Ooids typically form in warm, shallow marine environments that undergo moderate to high energy waves, such as intertidal settings. The movement of the waves is responsible for the repeated transport, burial, and accretion of the grain, while warmer waters enhance calcite supersaturation and lithification. It should be noted that as ooids age and continue to build layers, grains that exceed 2 mm in diameter are classified as pisoids and its associated sedimentary rock would be called a pisolite.