In case of marine sediments, ooze does not refer to a sediment's consistency, but to its composition, which directly reflects its origin. Ooze is pelagic sediment that consists of at least 30% of microscopic remains of either calcareous or siliceous planktonic debris organisms. The remainder typically consists almost entirely of clay minerals. As a result, the grain size of oozes is often bimodal with a well-defined biogenic silt- to sand-size fraction and siliciclastic clay-size fraction. Oozes can be defined by and classified according to the predominate organism that compose them. For example, there are diatom, coccolith, foraminifera, globigerina, pteropod, and radiolarian oozes. Oozes are also classified and named according to their mineralogy, i.e. calcareous or siliceous oozes. Whatever their composition, all oozes accumulate extremely slowly, at no more than a few centimeters per millennium.