Anglesey Mining said assay results from the latest three holes drilled at the Parys Mountain project in Wales showed multiple intercepts of various metals.
Best of the grades were zinc at 8.5%, 5.3% lead, copper at 1% and 0.8 grammes per tonne (g/t) gold.
The final two holes of the programme are now being logged for additional data to assist with geotechnical domain modelling, said the statement.
Jo Battershill, Anglesey’s chief executive, said: “The intention of this programme was to increase the amount of resources in the Indicated category for the White Rock deposit, which stood at 4.7Mt, or 79%, prior to commencing the drilling.
"Given the results, we are very confident that a significant portion of the currently Inferred material will be upgraded to Indicated.
"The importance of this should not be discounted given Inferred resources are not permitted to be included in reserve estimates.”
“The next stage of this programme is to conduct pre-concentration studies on representative samples from areas that are likely to be mined.
“In other areas, we continue to progress the ecological surveys required for the environmental baseline work and we will soon commence the initial tailings management and design studies.
“Both of these aspects are critical to progressing Parys Mountain through the permitting phase.”