Felsic, intermediate and mafic igneous rocks differ in their mineral composition. Felsic rocks are light in color and are composed of feldspars and silicates. Mafic rocks are darker and are composed of magnesium and iron. Intermediate rocks are composed of the minerals amphibole and feldspar and contain a combination of light and dark minerals.Know More
Igneous rocks are formed by the cooling and crystallization of magma. The temperature of cooling determines which types of minerals are found in the rock and helps scientists classify the rock as felsic, intermediate or mafic. Rocks that begin their cooling at low temperatures are rich in minerals containing silicon, potassium and aluminum. High temperature igneous rocks contain minerals higher in calcium, sodium, iron and magnesium. Ultramafic rocks are a fourth classification of igneous rock. These rocks are rare on the Earth's surface and contain low amounts of silica the minerals olivine, plagioclase feldspars and pyroxene.
The temperature of cooling igneous rock creates a difference in the texture of the rock. A gradual cooling of magma creates large crystals. Magma that cools fast produces smaller crystals. If volcanic magma cools very quickly on the Earth's surface, obsidian glass is the result. Obsidian glass contains no crystalline structures.Learn more in Earth Science
Fossils are primarily found in sedimentary rocks because these rocks form at low temperatures and pressures. Igneous rocks form at temperatures and pressures that are high enough to destroy any organic remains. On rare occasions, fossils are found in metamorphic rocks, but they are deformed by the heat and pressure.Full Answer >
A person who studies rocks is called a geologist. Geologists also study how the Earth is made and how the planet changes in time.Full Answer >
The characteristics of metamorphic rock are that some contain layers and streaks of different colors and textures caused by different minerals. Other metamorphic rocks are more uniform in color and texture and have minerals arranged in parallel layers.Full Answer >
Rocks are categorized into three types: igneous, sedimentary and metamorphic. They are mainly classified based on the processes they undergo during formation.Full Answer >