Classifications of limestone are based on the relative concentrations of micrite and sparite. These classifications are based on the idea that, in calm waters, tiny particles of lime mud are (1) available and (2) able to settle on the bottom and remain there, whereas in agitated waters, particles of microsize remain in suspension and are not deposited. Two problems limit this reasoning: (1) lime mud from low-energy deposits commonly filters into underlying high-energy deposits, or waters flowing through pores may effect such a transfer of lime mud, and (2) an even more complicated problem is the biochemical precipitation of cryptocrystalline cement in reefs. Cryptocrystalline cement that precipitates within millimeters to centimeters of the surfaces of reef rock looks jus like micrite. As bioerosion converts the solid colonies of reef organisms into skeletal particles that are cemented rapidly beneath the surfaces of the reef by cryptocrystalline cement, the unwary geologist is tempted to term reef rock a biomicrite or wackestone or complain the "the reef core is represented by lithified lime mud." Hence, case histories abound where unwary geologists confused reef rock for low-energy limemud facies.

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