Feldspar is a group of rock-forming minerals that make up about 60% of the Earth's crust. They are primarily composed of aluminum, silicon, and oxygen, and are classified into two main types: alkali feldspar and plagioclase. These minerals are essential in the formation of igneous, metamorphic, and sedimentary rocks. Feldspar is widely used in various industries, including ceramics, glassmaking, and as a filler in paints and plastics. Its abundance and versatility make it a crucial component in many geological processes and industrial applications, contributing to the development of materials we use every day.