Plutonic produced 19,232 ounces of gold in the March quarter from the milling of 343,932 tonnes at 2 grams per tonne gold.

Recoveries improved to 86% from 84% in the December quarter and 80% for 2017.

The company said recoveries had risen to 90% during April.

Superior president and CEO Chris Bradbrook said the increase in recoveries was achieved without the anticipated benefit from the gravity circuit that is currently being added to the mill.

"The ramp-up of quarterly production towards annual guidance proceeded as expected, with the first quarter anticipated to be the weakest of the year," he said.

"Underground stope grade was lower than previously experienced as we mined through lower grade material before reaching anticipated higher grades ...