Rocks are a natural aggregate of one or more minerals. The study of rocks draws upon mineralogy, geology, paleontology, chemistry, and physics. Mineral components and organic remains may be determined with the unaided eye, but often times positive identification will require high magnification or devices more sophisticated than a microscope. Texture refers to the size, shape, and arrangement of component constituents. Textural and structural terms may vary with different rock classifications.
Structures are usually visible on a geologic scale, whereas textures are on a hand specimen scale.
Texture is the result of the formational environments and structures, the result of deformations. There are three classifications of rocks found on Earth, igneous, sedimentary, and metamorphic. Earth is divided into a crust, mantle, and core, with the upper mantle and crust together referred to as the lithosphere. The lithosphere is divided into plates that are bounded by faults, subduction zones, and spreading centers. Therefore, igneous and metamorphic rocks dominate the lithosphere volumetrically and sedimentary rock is primarily exposed as a thin covering over much of the Earth's continents.