Gina Rinehart's Roy Hill appears to have exported less iron ore in the first three months of 2018 than in each of the previous two quarters, but the company says a rebound in performance in April has it back on track to achieve its full potential.

Roy Hill typically does not publish its export statistics, but its performance can be gleaned through a comparison of Port Hedland export data and the exports claimed by the other miners who use the port.