Igneous Rocks: The Three Different Types Of Rocks

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There are three different types of rocks. We should know about
• Igneous
• Sedimentary
• Metamorphic
Sedimentary rocks are made of fragments of other rocks; igneous, metamorphic or sedimentary. They are made when an older rock erodes or weathers to produce sediment, for instance sand on a beach. The sediment is then compacted and cemented together to produce a rock. Sedimentary rocks can also contain individual grains of minerals which have been eroded out of older rocks.
Igneous rocks are formed from the cooling of magma - molten rock. They are the rocks that form from volcanoes.
Metamorphic rocks are a result of heat and pressure on pre-existing rocks which undergo changes in the solid state. No melting occurs. They are associated with mountain
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A large portion of the granite is made of small crystals of orthoclase feldspar which give the rock the pink or reddish colour. Other minerals present are quartz (usually gray). albite feldspar (white) and either white mica (muscovite) or black mica (biotite). The word granite means grain-rock, it weathers, and it crumbles into loose grains.

7. Diorite Diorite is a coarse-grained igneous rock intermediate in composition between granite and gabbro. It can sometimes be described as a "white granite" because of the abundance of albite, a white feldspar. Depending upon the amount of iron rich minerals present, diorite can range from nearly white to quite dark. Diorite has the same mineral content as andesite.

8. Gabbro Gabbro is a dark, coarse-grained igneous rock. It has the same mineral content as basalt, but the grains in gabbro are visible to the naked eye.

9. Porphyry The term porphyry simply refers to the two distinctly different grain sizes present in an igneous rock. The larger crystals are called phenocrysts and the finer crystals are the groundmass. The groundmass can be rhyolite, andesite, or basalt and even, rarely, granite. The phenocrysts are often feldspar crystals or hornblende crystals.

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They are layered accumulations of sediments-fragments of rocks, minerals, or animal or plant material. Temperatures and pressures are low at the Earth's surface, and sedimentary rocks show this fact by their appearance and the minerals they contain. Most sedimentary rocks become cemented together by minerals and chemicals or are held together by electrical attraction; some, however, remain loose and unconsolidated. The layers are normally parallel or nearly parallel to the Earth's surface; if they are at high angles to the surface or are twisted or broken, some kind of Earth movement has occurred since the rock was formed. Sedimentary rocks are forming around us all the time. Sand and gravel on beaches or in river bars look like the sandstone and conglomerate they will become. Compacted and dried mud flats harden into shale. Scuba divers who have seen mud and shells settling on the floors of lagoons find it easy to understand how sedimentary rocks