Feldspar

Feldspar is the name given to a group of minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry. This group includes aluminum silicates of that contain calcium, sodium, or potassium. It is the single most abundant mineral group on Earth.
Feldspar is a common raw material used in glass making, ceramics, and to some extent as a filler and extender in paint, plastics, and rubber.