Zinc Blende (Sphalerite — ZnS) Structure

Structure type: Cubic close-packed (FCC) $S^{2-}$ lattice; $Zn^{2+}$ in half of tetrahedral holes Coordination: Both Zn and S are tetrahedrally coordinated (4-coordinate) Why froth flotation works: The $S^{2-}$ exposed at the surface creates a covalent, relatively non-polar surface — hydrophobic, attaches to pine oil.

Haematite (Fe2O3) Structure

Structure type: Corundum structure — hexagonal close-packed $O^{2-}$ lattice; $Fe^{3+}$ in 2/3 of octahedral holes Why hydraulic washing: High density (~5.3 g/$cm^{3}$) vs gangue (~2.6 g/$cm^{3}$) — large density difference drives separation.

NaCl (Rock Salt) Reference Structure

Structure type: Face-centered cubic; $Na^{+}$ and $Cl^{-}$ in alternating positions Coordination: 6:6 (octahedral) This is the reference ionic structure for halide ores like rock salt.