The distribution of initiation loads for cone cracking during Vickers indentation is studied by direct experimental observation of the indentation process and by simulation. Observations on three different glasses show that cone cracks initiate at the edge of the contact impression and yield distributions of initiation loads with nonzero minima. The simulations, based on a model of an expanding indentation impression in a random array of active crack nuclei, yield distributions of initiation loads with minima of zero. Cone cracks at sharp contacts are concluded to be initiated from nuclei generated by the contact process itself, rather than by nuclei preexisting on the contact surface.