Diamond films grown on molybdenum substrates are indented with conical diamond indenters to depths more than 5 times the thickness of the film. This causes delamination and spalling of the film. The effects of variations in indenter angle and film thickness are demonstrated. Using a radius of the delaminated area to the residual contact radius, sharper indenters are shown to cause a 10 to 20% change in that ratio. For films greater than 5 μm thick, there is no apparent film thickness effect. Possibilities for this observation are cracking due to bending stresses or the interfacial crack kinking out of the interface due to a reduction in compressive stresses, leading to mixed mode loading. The strain energy release rate of the interface for an 800 nm diamond film on molybdenum is between 2.4 and 7 J/m2.