Both the oceanic and continental crusts are partly covered with a thin layer of sedimentary rocks and sediments. These consist mainly of clastic rocks such as sandstone, siltstone and shale, along with carbonate rocks such as dolostone and limestone. These clastic rocks are composed of mainly quartz, clay minerals, and a small amount of micas and feldspar minerals. The carbonate…

As a second example, let’s consider the rocks of the continental crust. The continental crust is made up mainly of rocks with a granitic to andesitic composition. These rocks are composed mainly of alkali feldspar, quartz, and plagioclase feldspar, with smaller amounts of amphiboles and micas. This small number of minerals makes up most of the continental crust.

As an example of the influence of just a few minerals, let’s consider the rocks of the oceanic crust. The oceanic crust is mainly composed of basalt and gabbro. These two rock types are made up of mainly of plagioclase feldspar and pyroxenes, with smaller amounts of olivine, micas and amphiboles. This small group of minerals makes up most of…

Scientists have identified over 4,000 different minerals. A small group of these minerals make up almost 90% of the rocks of Earth’s crust. These minerals are known as the common rock-forming minerals. To be considered a common rock-forming mineral, a mineral must: A) be one of the most abundant minerals in Earth’s crust; B) be one of the original minerals present at…