# Rudite

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**Rudite** is a general name used for a [sedimentary rock](/source/Sedimentary_rock) composed of rounded or angular [detrital](/source/Detritus) grains, i.e. [granules](/source/Granule_(geology)), [pebbles](/source/Pebble), [cobbles](/source/Cobble_(geology)), and [boulders](/source/Boulder), which are coarser than [sand](/source/Sand) in [size](/source/Particle_size_(grain_size)). Rudites include sedimentary rocks composed of both [siliciclastic](/source/Siliciclastic), i.e. [conglomerate](/source/Conglomerate_(geology)) and [breccia](/source/Breccia), and [carbonate](/source/Carbonate_rock) grains, i.e. [calcirudite](/source/Calcirudite) and [rudstone](/source/Rudstone). This term is equivalent to the Greek-derived term, [psephite](/source/Psephite). Rudite was initially proposed by Grabau[1] as "rudyte". It is derived from the Latin word *rudus* for "crushed stone", "rubbish", "debris", and "rubble".[2][3][4]

Rudites can be deposited in a variety of nonmarine and marine environments. In nonmarine settings, gravels, which later were lithified to become rudites, accumulated within fluvial channels, within alluvial fans, and as glacial deposits. In marine environments, rudites were deposited along [shorelines](/source/Shoreline) as part of [beaches](/source/Beach), as basal conglomerates during [marine transgressions](/source/Marine_transgression), and in the deep sea by slumps and [turbidites](/source/Turbidite). Rudites composed largely of rounded siliciclastic gravel are conglomerates and others composed of angular siliciclastic gravel are breccias.

Pettijohn [5] gives the following descriptive terms based on grain size, avoiding the use of terms such as [clay](/source/Clay) or [argillaceous](/source/Argillite) which carry an implication of chemical composition. The Greek terms are more commonly used for metamorphosed rocks, and the Latin for unmetamorphosed:

Descriptive size terms Texture Common Greek Latin Coarse gravel(ly) psephite (psephitic) rudite (rudaceous) Medium sand(y) psammite (psammitic) arenite (arenaceous) Fine clay(ey) pelite (pelitic) lutite (lutaceous)

## References

1. Grabau, A.W. (1904) *On the classification of sedimentary rocks.* American Geologist. vol. 33, pp. 228-247.

1. U.S. Bureau of Mines Staff (1996) *Dictionary of Mining, Mineral, & Related Terms.* Report SP-96-1, U.S. Department of Interior, U.S. Bureau of Mines, Washington, D.C.

1. 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

1. [Pettijohn F. J.](/source/Francis_J._Pettijohn) (1975), *Sedimentary Rocks*, Harper & Row, ISBN 0-06-045191-2

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