The company said measured and indicated tonnes at Empire were now 19.3 million tonnes with copper content up 11% to 81,948t, zinc content up 26% to 37,650t, 13% more silver for 6.82 million ounces, and gold content now estimated at 217,500oz.

"I am pleased to report this significant increase to our Empire polymetallic openpit resource. As we stated throughout 2019 and early 2020, our team has continued work on the main Empire orebody at the same time as we are moving forward at the Red Star project," said CEO Ryan McDermott.

Phoenix is reconsidering the metallurgical processing route from just a copper solvent extraction-electrowinning plant with a bleed stream producing a zinc concentrate, to one taking the leached material and re-leaching it with cyanide and using Merrill Crowe recovery, because of the relatively high silver content, to optimise gold and silver recoveries.

The company has also recently started drilling the neighbouring Red Star silver-lead deposit.

The company's shares (PXC:LSE) closed down 15% Monday at 17.5p, having risen to an intra-day high of 23.94p. The stock's 12-month low point was 4.5p.