good quality, best price, prompt delivery 1. Feldspar FELDSPAR comprises a group of minerals containing potassium, sodium, calcium and aluminium silicates. They are the most common rock-forming minerals.NameFormula SiO2Al2O3K2ONa2OCaOBaOSpecific DensityHardnessTypeColorPotassiumFeldspar K2O·Al2O3·6SiO27016942.566orthoclaseWhite, pink, milky whiteSodium feldsparNa2O·Al2O3·6SiO263-7016-20≤1≥82. ...