The AIM-listed miner said an appraisal of past exploration at Copperhead had revealed an estimate of copper content of 35mln tonnes at 0.16% Cu for 56,000 tonnes of copper according to calculations from the Carpentaria Exploration Company in 1972.
However, the company said that this estimate was historical and had been calculated before the introduction of the JORC code, but added that subsequent core sampling in 1988 had raised the average core grade to 0.25% Cu.
Rockfire also said that it was planning induced polarisation geophysics to help target potential extensions and high-grade zones at the project as well as drilling to verify and expand the historical results and establish a mineral resource.
David Price, chief executive, said: "The grades achieved by Carpentaria in its core sampling don't take into account any shears or fault zones which could enhance the overall grade of the system. In 1988, Costain Australia located the original core drilled by Carpentaria and assayed portions of the core not previously analysed. This second phase (in-fill) core analysis returned grades up to peak values of 2.81% Cu and 1.54% Mo. This subsequent sampling, lifted the overall grade to achieve an average core sampling grade of 0.25% Cu.
He added: “Based on a combination of soil, rock, auger and diamond drilling (with an average of all core assays being 0.25% Cu), the Company believes that Copperhead presents an initial exploration target of 60MT - 75MT, at grades of between 0.15% Cu and 0.20% Cu, and with material silver and molybdenum credits. This exploration target is for the potential delineation of 90,000 - 150,000 tonnes of copper metal.”
In late-afternoon trading Monday, Rockfire shares were up 13% at 1.9p.