Nov 16, 2008· The rock in a lead ore deposit contains 84% PbS by mass. How many kilograms of the rock must be processed to o? The rock in a lead ore deposit contains 84% PBS by mass. How many kg rock be processed to obtain kg of PB? A rock in a lead ore has 84% PbS by mass. How many kg of the rock must be processed to obtain kg of Pb?