Aquila improves recoveries at Michigan-based Back Forty project

TORONTO (miningweekly.com) – After completing comprehensive and integrated metallurgical testwork, TSX-listed project developer Aquila Resources on Monday reported that it had improved recoveries and the potential for increased production of its flagship Back Forty project's two main metals, gold and zinc.

Gold recoveries improved to 63%, up from 61%, and zinc recoveries improved to 93%, up from 91%, when benchmarked against the company's June 2014 preliminary economic assessment (PEA).

"We are encouraged by the positive results of our metallurgical test programme. Improved recoveries for gold and zinc clearly suggest the potential for improved metal production and ultimately improved economics at Back Forty. 

“We will be further quantifying and evaluating the impact of these results on Back Forty's project economics during the course of our work on the feasibility study, which is being developed in parallel with our permitting activities, both of which are expected to be completed before the end of 2016,” advised Aquila VP for project development Andrew Boushy.

The metallurgical testwork, which was conducted by SGS Canada, in Lakefield, analysed new representative samples indicating that the mineral resource was an aggregate of four metallurgical zones, namely three sulphide zones (Main, Pinwheel and Tuff) and one oxide zone. 

Further testwork performed on composite samples for each of these ore types revealed a gradient, with higher-grade samples generally exhibiting improved recovery compared with lower-grade samples. When new recovery equations were applied to the PEA mine plan, the impact on recovery ranged from a 2% improvement for zinc to a 15% improvement for silver.

Testwork also demonstrated that more gold and silver could be recovered from the zinc concentrate. Additional work would be performed to determine whether the concentration of precious metals in zinc concentrate would meet the required payable threshold.

Aquila stated that the positive results of the metallurgical test programme provided the company with the basis to finalise its process design, a key step in the development of the Back Forty feasibility study. Aquila expected to complete the feasibility study, including an updated resource and mine plan, by December.

Lycopodium Minerals Canada was currently designing the processing plant and provided input for the comminution testwork.