Original: Feldspars (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8) are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust.
Simplified: Feldspar is the name of a group of rock-forming minerals that make up as much as 60% of the Earth's crust.