Feldspar exists in different phases such as microcline, albite and anorthosilicate. The feldspar has an average chemical composition of 62% SiO 2, 26% Al 2 O 3, 8% K 2 O, 3% Na 2 O and 1% CaO as the main constituents. ... roasting tem- ltd., Kolkata-India) followed by roll crusher (Rajco Science and perature, roasting time, amounts of ...