Calcilutite

 Calcilutite (also known as cementstone[1]) is a type of limestone that is composed of predominantly, more than 50 percent, of either clay-size or both silt-size and clay-size detrital (transported) carbonate grains. These grains consist either of fossil fragments, ooidsintraclastspellets, other grains, or some combination of them. The term calcilutite was originally proposed in 1903 by Grabau[2][3] as a part of his calcilutite, calcarenite and calcirudite classification system based upon the size of the detrital grains composing a limestone.[4][5] In the original classification[2][3] of limestone according to the dominant grain-size, calcisiltites were not named and are classified as calcilutite. In this classification, which the majority of geologists follow, a calcilutite consists of both silt- and clay-size, less than 0.062 mm in diameter, grains. It is the carbonate equivalent of a mudstone (not to be confused with a 'mudstone' of the Dunham Limestone classification).[5][6] Calcilutites can accumulate in a wide variety of marine and lacustrine environments.[5][7]

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