Rudite is a general name used for a

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

composed of rounded or angular

detrital Detritus (; adj. ''detrital'' ) is particles of rock derived from pre-existing rock through weathering and erosion.Essentials of Geology, 3rd Ed, Stephen Marshak, p G-7 A fragment of detritus is called a clast.Essentials of Geology, 3rd Ed, Steph ...

grains, i.e. granules,

pebble A pebble is a clast of rock with a particle size of based on the Udden-Wentworth scale of sedimentology. Pebbles are generally considered larger than granules ( in diameter) and smaller than cobbles ( in diameter). A rock made predominan ...

s, cobbles, and

boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

s, which are coarser than

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of ...

size Size in general is the magnitude or dimensions of a thing. More specifically, ''geometrical size'' (or ''spatial size'') can refer to linear dimensions (length, width, height, diameter, perimeter), area, or volume. Size can also be meas ...

. Rudites include sedimentary rocks composed of both

siliciclastic Siliciclastic (or ''siliclastic'') rocks are clastic non carbonate sedimentary rocks that are composed primarily of silicate minerals, such as quartz or clay minerals. Siliciclasic rock types include mudrock, sandstone Sandstone is a clasti ...

, i.e. conglomerate and

breccia Breccia () is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language, in whi ...

, and

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

grains, i.e. calcirudite and rudstone. This term is equivalent to the Greek-derived term, psephite. Rudite was initially proposed by GrabauGrabau, A.W. (1904) ''On the classification of sedimentary rocks.'' American Geologist. vol. 33, pp. 228-247. as "rudyte." It is derived from the Latin word ''rudus'' for "crushed stone," "rubbish," "debris," and "rubble".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.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. 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

shoreline A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water pa ...

s as part of

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells ...

es, as basal conglomerates during

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

s, and in the deep sea by slumps and

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites were ...

s. Rudites composed largely of rounded siliciclastic gravel are conglomerates and others composed of angular siliciclastic gravel are breccias. Pettijohn Pettijohn F. J. (1975), ''Sedimentary Rocks'', Harper & Row, gives the following descriptive terms based on grain size, avoiding the use of terms such as

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...

argillaceous Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minera ...

which carry an implication of chemical composition. The Greek terms are more commonly used for metamorphosed rocks, and the Latin for unmetamorphosed:

References

{{reflist Sedimentary rocks