Gibraltar ups minable reserves at Lomas Bayas copper property

Minable reserves at the Lomas Bayas property 110 km from Antofagasta in northern Chile are on the rise.

Gibraltar Mines (TSE) now estimates proven and probable minable reserves at 283.7 million tonnes grading 0.36% copper at a stripping ratio of 0.4-to-1.

The total is broken down into heap-leach ore and run-of-mine leach ore.

Heap-leach reserves, at a cutoff of 0.27% copper, total 131 million tonnes grading 0.533% copper. Run-of-mine leach reserves, at a cutoff of 0.08% copper, total 152.7 million tonnes grading 0.219% copper.

A further geological resource is estimated at 741.2 million tonnes grading 0.3% copper. The geological resource includes: 69.4 million tonnes grading 0.254% copper (0.08% cutoff) within the pit limits; 369.5 million tonnes grading 0.285% copper (0.2% cutoff) around and below the pit; 133.5 million tonnes grading 0.275% copper (0.2% cut-off) in Lomas East; and 168.8 million tonnes grading 0.37% copper (0.2% cut-off) in Fortuna de Cobre.

Lomas Bayas was last estimated to contain a preliminary resource totaling 170.8 million tonnes grading 0.46% copper. The total included 80.1 million tonnes grading 0.68% copper (based on a 0.36% cutoff) plus 90.7 million tonnes grading 0.27% copper (0.2% cutoff).

Gibraltar expects to complete a feasibility study at Lomas Bayas by year-end.

Previous scoping studies estimated that a 20,000-tonne-per-year mining, crushing and heap-leaching operation would produce 100 million lb. of copper per year.

The preliminary study projected the capital cost of the operation at US$156.5 million, while cash costs were estimated at US52 cents per lb.

Those output and cost projections are expected to change with the new feasibility and the inclusion of run-of-mine leaching.

In preparation for financing the new project, Gibraltar has completed a $73.75 million equity issue, and preliminary discussions with potential lenders have already started.