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Uluru (Ayers Rock) is a large sandstone formation in Northern Territory, Australia.. Sedimentary rocks can be subdivided into four groups based on the processes responsible for their formation: clastic sedimentary rocks, biochemical (biogenic) sedimentary rocks, chemical sedimentary rocks, and a fourth category for "other" sedimentary rocks formed by impacts, volcanism, and other minor processes.
Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was formed. This process is called metamorphism, meaning to "change in form". The result is a profound change in physical properties ...
In sedimentary geology, maturity describes the composition and texture of grains in clastic rocks, most typically sandstones, resulting from different amounts of sediment transportation. A sediment is mature when the grains in a sediment become well-sorted and well-rounded due to weathering or abrasion of the grains during transport.
Clastic rocks are classified according to their predominant grain size and their composition. In the past, the term "Clastic Sedimentary Rocks" were used to describe silica-rich clastic sedimentary rocks, however there have been cases of clastic carbonate rocks. The more appropriate term is siliciclastic sedimentary rocks.
A conglomerate or any clastic sedimentary rock that consists of a single rock or mineral is known as either a monomict, monomictic, oligomict, or oligomictic conglomerate. If the conglomerate consists of two or more different types of rocks, minerals, or combination of both, it is known as either a polymict or polymictic conglomerate.
About 40% of minerals in sedimentary rocks are clays and clays are the dominant minerals in the most common sedimentary rocks, mudrocks. [32] They are also an important component of soils. [32] Feldspar that has been replaced by clay looks chalky compared to more crystalline and glassy unweathered feldspar grains. [33]
The other minerals in the rock are termed accessory minerals, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon. [34] [38]
Ironstones consist of 15% iron or more in composition. This is necessary for the rock to even be considered an iron-rich sedimentary rock. Generally, they are from the Phanerozoic which means that they range in age from the present to 540 million years ago. [1] They can contain iron minerals from the following groups: oxides, carbonates, and ...