Silicon slag is a by-product of the production and refining of commercial silicon. It is a glassy, brittle material of dark green colour interspersed with silicon particles.
The average composition of slag is
Si 20–30 %, SiO2 5–20 %, SiC 20–40 %, CaO 25–40 %, Al2O3 3–35 %
It is used in ferrous metallurgy as a deoxidizer and also as a desulfurization agent, in Silico Manganese production, road construction and also in cement, concrete, calcium silicate board and permeable brick industry.