Geology of solar terrestrial planets is basalt, a denser volcanic rock that is the primary constituent of the ocean floors. Sedimentary rock is formed from the accumulation of sediment that becomes compacted together. Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form only about 5% of the crust. The third form of rock material found on Earth is metamorphic rock, which is created from the transformation of pre-existing rock types through high pressures, high temperatures, or both. The most abundant silicate minerals on the Earth's surface include quartz, the feldspars, amphibole, mica, pyroxene, and olivine. Common carbonate minerals include calcite
Silicate minerals Silicate minerals Silicate minerals are rock-forming minerals with predominantly silicate anions. They are the largest and most important class of rock-forming minerals and make up approximately 90 percent of the Earth's crust. In mineralogy, silica, or silicon dioxide SiO, which corresponds to "x"=2 in the general formula, is usually considered a silicate mineral—even though its silicate "anion" has no negative charge and it has no cations. Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes