What is feldspar used for? - QuoraFeldspar has multiple uses across various industries. Glass Industry: Feldspar is used in Glass Industry for - 1. Due to its Alumina content which provide gl.what is feldspar used for,Feldspar minerals make up over 50% of Earth's crust. - GeologyFeldspar minerals occur in igneous, metamorphic and sedimentary rocks throughout the world. They are used to make glass, ceramics, paint, plastics, rubber.