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Quartz, feldspar and mica are some of the most abundant minerals in the earth's crust.Quartz (SiO2) is present in almost all rocks. It is hard, resistant to chemical weathering and has no cleavage, which means it is also resistant to physical weathering. It is abundant in silica-rich igneous rocks, like granite and rhyolite. Because it is so resistant to erosion, it is also found in most sedimentary rocks (even if as very small grains). It is pervasive in most metamorphic rocks.Feldspar (K,Na,Ca)(AlSiO4) is probably the most common mineral in the earth's crust. They are present in abundance in all and in many igneous rocks. Feldspars are susceptible to both chemical and physical weathering, breaking down into clays. Mica is really a whole host of minerals, muscovite, biotite and chlorite being the most common. Mica is soft and can be distinghed by it perfect cleavage, which means the mineral breaks into very thin sheets. It is easily eroded to form clay minerals. Mica is abundant in silicic igneous rocks and is the main component of many metamorphic rocks (add enough heat and pressure to clay and it becomes mica). Schist is a metamorphic rock composed almost entirely of mica.
so would mica be abundent in like slate? for example, but have little feldspar, where clay if mainly feldspar with alittle quartz, and granite would be quartz and mica, with little feldspar?