Microwave Assisted Breakage Through Quartz Inversion in Low Grade Iron Ore

Indian low grade iron ores contains quartz as gangue bearing mineral with poor liberation characterstics. Banded iron formations such as Banded Hematite Jasper has alternate layers of Hematite, Quartz considered to be hard ore. The presence of quartz in low grade iron ore causes the breakage at mineral - gangue interface selectively during its inversion by microwave treatment. The present study revealed the crack propogation mechanism is due to quartz transition from α to β phase (volumetric expansion). Detail studies showed that crack propogation can reduce energy consumption during grinding and impove liberation of ore. Hardness and compressive strength of ore are reduced from 925 to 825 HV (hematite), 1660 to 1120 HV (quartz) and 5 to 2 kN/cm² respectively. The effect of inversion and simultaneous recrystallization to form new born hematite grains is showed during flotation of iron ore. Fe(T) is upgraded from 50% to 59% and quartz from 25% to 12% respectively for flotation concentrate.