Summary: An investigation of the system Cu-Fe-O has established the existence of a phase near 3Cu₂O.Fe₃O₄ and the non-existence of Cu₂O.Fe₂O₃ a in the system over the range of oxygen pressures investigated.

The X-ray diffraction patterns obtained from four samples of natural delafossite have been found to be similar to that obtained from a synthetic sample of the 3Cu₂O.Fe₃O₄ phase. It has also been shown that, when heated under equilibrium conditions in the thermobalance in air, a sample of natural delafossite and the synthetic 3Cu₂O.Fe₃O₄ behaved similarly.