how many types of rocks make up the earth's crust
Crust (geology) The continental crust has an average composition similar to that of andesite.[13] The most abundant minerals in Earth's continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, and pyroxenes at 11%.[14] Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle. Although the continental crust comprises only about 0.6 weight percent of the silicate on Earth, it contains 20% to 70% of the incompatible elements.
Oceanic crust Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or [er it is denser, having a mean density of about 2.9 grams per cubic centimeter[1] as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter.[2]