The emerging gold miner said a highlight was 12.2m at 11.76g/t gold, including 3m at 38.3g/t, indicated the zone was higher grade and thicker than first thought.
Copperstone has a 2018 proven and probable reserve of 175,093 ounces grading 6.79g/t, supporting an estimated mine life of 4.5 years.
Kerr is targeting a proven and probable reserve of 320,000oz to take the mine life beyond eight years.
It is aiming to get the previously-mined Copperstone back into production by the fourth quarter.
It signed a term sheet for up to US$25 million in project financing with Sprott Private Resource Lending last year, ending discussions with Pandion Mine Finance over a possible $27.6 million package.
A prefeasibility study last year put initial capex at $22.7 million, the internal rate of return at 40% and all-in sustaining costs at $875/oz.
Kerr had C$3 million (US$2.2 million) in cash and investments at the end of December.
Its shares are trading at the lower end of its 52-week range of C10.5c-25c, last trading at 12.5c to capitalise it at $34.6 million.
