Anorthosite is a type of igneous rock primarily composed of plagioclase feldspar, which gives it a light color. It typically forms in large, layered intrusions and is found in the Earth's crust, particularly in regions like the Moon and Greenland. Anorthosite is significant in geology because it provides insights into the processes that shape planetary bodies. This rock is often associated with the Lunar Highlands, where it is believed to have formed from the cooling of magma. Anorthosite can also be found on Earth in ancient crustal formations, making it an important subject of study for understanding the planet's geological history.