A thermodynamic, corrosion, potentiometric and voltammetric study of t
he behaviour of diamonds in halide, halide-oxide and oxide melts has b
een carried out. To account for the rise of surface conductance in dia
mond crystals when they are in contact with melts of definite composit
ion, a concept of electrochemical potential and equilibrium due to red
ox processes occurring at the diamond-melt interface is developed.