Silicates are the most abundant group of minerals found in Earth's crust, according to Georgia State University. The most abundant elements in the Earth's crust are oxygen at 46.6 percent and silicon at 27.7 percent. These two elements combine with each other and other elements to form various silicates.
Silicates are categorized by their chemical composition or their crystal structures. The most abundant specific silicates in the Earth's crust are feldspars (primarily orthoclase and plagioclase) and quartz, which together make up 95 percent of the continental crust rocks. Other silicates include olivine, hornblende (known as the amphibole group), augite (known as the pyroxene group) and micas.