Calcirudite is a type of limestone that is composed predominantly, more than 50 percent, of carbonate grains that are larger in size than sand (2 mm in diameter). The grains can consist of either fragments of fossils, fragments of older limestones and dolomites, other carbonate grains, or some combination of these. The term calcirudite was originally proposed in 1903 by Grabau[1][2] as a part of his calcilutite, calcarenite and calcirudite classification system based upon the size of the detrital grains composing a limestone.[3][4] Depending on roundness of the grains, calcirudite is the carbonate equivalent of either a breccia, in the case of predominantly angular grains, or conglomerate, in the case of predominantly rounded grains. Calcirudites can accumulate in a wide variety of coastal, lacustrine, and marine environments.[4][5]

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  1. Grabau, A.W. (1903) Paleozoic coral reefs. Geological Society of America Bulletin. vol. 14, pp. 337-352.
  2. Grabau, A.W. (1904) On the classification of sedimentary rocks. American Geologist. vol. 33, pp. 228-247.
  3. Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ISBN 0-922152-76-4
  4. 4.0 4.1 Flügel, E. (2010) Microfacies of Carbonate Rocks, 2nd ed. Springer-Verlag Berlin, Germany. 976 pp. ISBN 978-3-540-22016-9
  5. Scholle, P.A., D.G. Bebout, and C.H. Moore (1983) Carbonate Depositional Environments. Memoir no. 33. Tulsa, Oklahoma, American Association of Petroleum Geologists. 708 pp. ISBN 978-0-89181-310-1