Introduction to Mineral Processing 5 3.0 Liberation and Comminution 3.1 Liberation In order to separate the minerals from gangue (the waste minerals) it is necessary to crush and grind the rock to unlock 3 cleavage planes (not 90) valuable minerals so that they are partially or fully exposed.Mineral (Carbonate) Not metallic -- Bubbles in HCL. Double refraction (2 images visible through clear sample). Rhombs,