Consisting substantially of silica (SiO2), which is the basis of most glasses. It provides silicon oxide.
Mineral composed of calcium carbonate (CaCO3), which is mined, crushed and ground until obtaining the desired grain size distribution. It provides calcium oxide (CaO) to the glass.
The same limestone family, however, the formulation consists of a double carbonate of calcium and magnesium.
It is a mineral consisting of an aluminum sodium silicate and potassium. The reason for its use is the source of aluminum oxide or alumina (Al2O3).