3. The silica deficient mineral is: B. Feldspar A. Olivine C. Feldspathoid D. Amphibole (BHU-2013)
Answer should be Olivine na??b/c olivine crystallizes earliest from magma and feldspars,quartz ,feldspathoids crystallize last .Also It is known that Silica content increases going down the Bowens rxn series.
hence olivine should be silica poor and others are relatively silica rich ,,as usual as I have been taught. BUT ANSWER IS FELDSPATHOID..??HOW