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Texture
texture
shale
Grain size
Pearls are formed within the soft tissue of mollusks, and start as a grain of sand. The mollusk concretes thin layers of calcium carbonate over the grain of sand. Therefore, a pearl would be considered sedimentary.
Texture
texture
texture
An arenite is a sedimentary rock with a grain size in the sand range on the Wentworth scale.
The Wentworth Scale commonly measures grains of boulders, cobble, gravel, pebbles, sand, silt, clay and calloid.
shale
texture
The name of sedimentary rock is usually based on it's grain size.
Rocks that are categorized as sedimentary rocks include sandstone, breccia shale, limestone and selenite. Sedimentary rocks are classified by their grain size.
Grain size
Pearls are formed within the soft tissue of mollusks, and start as a grain of sand. The mollusk concretes thin layers of calcium carbonate over the grain of sand. Therefore, a pearl would be considered sedimentary.
== == The "coarseness" of a sedimentary rock refers to the rock's textural character, and more particularly, the size of grains contained within it. Thus, a conglomerate containing pebble or cobble clasts is coarser than a sandstone containing sand grains. In the same way, a conglomerate containing boulders is coarser than a conglomerate containing pebbles. Clastic sedimentary rocks are classified using the Wentworth Scale. The coarsest elements of this scale are the Rudites. Boulder rudites are conglomeratic rocks with grains of diameter greater than 256mm. They are the coarsest element described on the Wentworth Scale. There is no upper limit to the scale of sedimentary coarseness, since the size of clast which can be preserved in a sedimentary rocks is potentially very large. 'Olistolith' is a term which describes very large clasts often derived from the sub-sea collapse of oversteepened slopes such as are found at continental margins. Sediments containing olistoliths may reasonably be described as the coarsest sedimentary rocks.