28. Solving a chemistry problem

70. Flotation is based on the fact that particles crushed from 0.1 to 0.3 mm in diameter sink when wetted and float when not wetted, regardless of the density of the material. Using the reference tables in the appendix, indicate which material will remain in the sludge and which will be removed with foam when separating: a) coal and mica; b) mixtures of pyrite and gypsum.