Vancouver-based Curis Resources (TSE:CUV) unveiled Thursday updated metallurgical results on samples from its Florence copper property in Arizona, showing an average copper extraction rate of 61 per cent - higher than the rate used in prior modelling.
The company said today that 16 in-situ recovery tests were done, with copper extraction ranging from 33 to 89 per cent.
The results follow news from earlier this month, when Curis secured an operating permit from the state of Arizona for its Florence copper project, calling it a "key milestone" in the construction and development of the site.
Optimal copper test extractions of over 70 per cent were reached, Curis said today, by using mid-range (10 g/l) H2SO4 concentrations, which is consistent with earlier test work by both the company and prior owner, BHP Copper.
The September 2010 preliminary economic assessment on the project used an average total copper recovery rate of just 49 per cent, which means the property's economics stand to improve.
"We are very pleased with the outcome of this next phase of critically important metallurgical test work at Florence Copper," said VP of technical services and environment with Curis, Dan Johnson.
"These results further confirm that there is tremendous potential to improve on the copper recoveries from historical estimates, and on the overall robust economics indicated in the PEA for this world-class in situ copper recovery project."
The goal of the on-going in-situ recovery test program is to represent a cross-section through a typical mineralized block in the deposit, and simulate in-situ treatment of the Florence copper mineralized resource.
This is done by allowing recovery solutions to flow horizontally through intact pieces of drill core using a specially designed laboratory apparatus.
"I remain convinced that the core box approach [used by Curis] toward ISR [in-situ recovery] simulation is more realistic than the vertical column method that has been used in the past and that it will enable a reliable projection of well field performance," said Dr. Terry McNulty, dubbed a metallurgical specialist by Curis, and the designer of the test program.
Curis said Thursday the next step in the metallurgical testing program will be to have these results included in an overall assessment of predicted ultimate copper recoveries.
Metallurgical testing at the project to improve on historical copper recovery estimates began in June of last year.
Earlier in 2012, Curis reported bottle roll test results on 16 initial samples from a 2011 core drilling campaign, along with laboratory scale in-situ recovery test results for four of these samples, with the remaining 12 reported today.
Johnson said these results suggest a mid-range sulfuric acid feed of between 8-10 g/L is likely to be optimal for the project to achieve "maximum possible recoveries".
Indeed, for every percentage increase of copper recovery, higher revenues will be generated from the project, which now has an estimated after-tax net present value of $360 million at a 7.5 per cent discount rate and a $2.50 per pound copper price.
The company in late September received the Aquifer Protection Permit from the State of Arizona's Department of Environmental Quality (ADEQ), which applies to the design, operation and closure of its phase 1 operations at the site.
The permit received authorizes the construction, operation and closure of a 24-well in-situ copper recovery operation - phase 1 - at the project in Florence, Arizona.
The recovery operation will be accompanied by an art solvent extraction/electrowinning facility that is designed to produce 99.999% pure copper cathode sheets, Curis said.
The in-situ recovery process requires no movement of rock or overburden, and there is therefore a substantially smaller footprint, with much less of an environmental impact on the surrounding area than with more traditional open pit mining operations.
The technique also requires substantially less mechanical energy in the form of trucks and explosives, and therefore generates significantly lower operating and capital costs.
According to the latest timeline, the company could begin full commercial production by early 2015, after which it expects to produce between 55 and 84 million pounds of copper per year.