Rocks are all around us. They make up the backbones of hills and mountains and the foundations of plains and valleys. Beneath the soil you walk on and the deep layers of soft mud that cover the ocean basins is a basement of hard rock.
Rocks are made up mostly of crystals of different kinds of minerals, or broken pieces of crystals, or broken pieces of rocks. Some rocks are made of the shells of once-living animals, or of compressed pieces of plants.
Igneous rocks make up approximately ninety-five percent of the upper part of the Earth's crust, but their great abundance is hidden on the Earth's surface by a relatively thin but widespread layer of sedimentary and metamorphic rocks.
Intrusive igneous rocks are formed from magma that cools and solidifies within the earth. Surrounded by pre-existing rock (called country rock), the magma cools slowly, and as a result these rocks are coarse grained. The mineral grains in such rocks can generally be identified with the naked eye.
Igneous rocks are crystalline or glassy rocks formed by the cooling and solidification of molten magma. Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary.
Igneous rocks are formed from the solidification of magma, which is a hot (600 deg.C - 1300 deg.C, or 1100 deg. - 2400 deg. F) molten or partially molten rock material. The Earth is composed predominantly of a large mass of igneous rock with a very thin covering of sedimentary rock. Whereas sedimentary rocks are produced by processes operating mainly at the Earth's surface such as weathering and erosion, igneous--and metamorphic--rocks are formed by internal processes that cannot be directly observed.
Igneous rocks are called fire rocks and are formed either underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped in small pockets. As these pockets of magma cool slowly underground, the magma becomes igneous rocks.
Igneous rocks are also formed when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. Igneous rocks are formed as the lava cools above ground.
Minerals are all over the place in your food in the glowed . A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. A rock, by comparison, is an aggregate of minerals and need not have a specific chemical composition. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms.  The study of minerals is called mineralogy.
Rocks are divided into three basic types, igneous, sedimentary and metamorphic , depending upon how they were formed. Plate tectonics provides an explanation for how rocks are recycled from igneous to sedimentary to metamorphic and back to igneous again.