Sedimentary Rocks:
Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles (detritus) to settle in place.
Sedimentary rocks are made when sand, mud and pebbles get laid down in layers. Over time, these layers are squashed under more and more layers. Eventually, the layers are lithified – turned to rock. Sedimentary rocks can be formed in deserts , lakes, rivers and seas .
There are three types of sedimentary rocks, they are:
Clastic sedimentary rocks- Clastic sedimentary rocks are composed of other rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock (lithic) fragments, clay minerals, and mica; any type of mineral may be present, but they in general represent the minerals that exist locally.
Biological sedimentary rocks- Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue.
Chemical sedimentary rocks- Chemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate. Common chemical sedimentary rocks include oolitic limestone and rocks composed of evaporite minerals, such as halite (rock salt), sylvite, barite and gypsum.
The main sedimentary rocks are conglomerate, breccia, sandstone, siltstone, shale, limestone, dolomite, gypsum, salt, chert, coal and amber.
LimestoneLimestone is a sedimentary rock, about 10% of sedimentary rocks are limestone, they are mostly used for building materials, for rock gardens, base of roads. Limestone is used pretty much everywhere; we have some at the school near the year 7 area.
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ShaleShale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call mud. Shale is the world’s most important oil and natural gas deposits.
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