Baja completes infill drilling program at Boleo

Vancouver — Baja Mining (BAJ-V, BAJFF-O) has completed the first 20,000 metres of an ongoing infill drill program at its Boleo copper-cobalt-manganese-zinc project despite delays caused by Hurricane John, which passed over Mexico’s Baja Peninsula in late August and early September.

The company’s equipment and facilities were not damaged in the storm, but the nearby towns of Santa Rosalia and Mulege were declared disaster zones by the Mexican government. The fresh water supply was lost, the sewage system was blocked, and streets and roads were flooded by heavy rains and strewn with large rocks and boulders. Baja Mining stopped its drills and deployed crews, trucks and equipment to help with the clean-up and medical relief process, earning the gratitude of local residents in the process.

With both towns back in business, the company is continuing the balance of its 38,000-metre infill drilling campaign at the project, situated near Santa Rosalia, Baja California Sur. The 20,000 metres completed to date are deemed sufficient to meet the requirements of the definitive feasibility study scheduled for completion in the fourth quarter of this year.

Baja Mining acquired rights to the Boleo project in early 2004, and has since focused its efforts on restoring the historic Mexican mine to producing status. Boleo was first exploited in 1868, and produced about 19 million tonnes at an average grade of 4.3% copper until 1972, with much higher grades (up to 24% copper) in the initial years. No attempt was ever made to recover the contained cobalt, zinc, or other potentially valuable minerals. Previous operators were unable to concentrate the minerals contained within the copper ore, which was direct smelted, thus requiring high cutoff grades. Material grading less than 3% copper was either not mined, or was used to backfill mined areas.

In more recent times, previous operators spent about US$25 million to assess reserves and develop modern mining and processing plans to extract the contained copper, cobalt and zinc. This work culminated in a 2002 prefeasibility study, which envisioned open-pit mining to address ground-control challenges, and solid liquid separation technology to separate the metal-enriched leach solutions from the clay-rich gangue material.

Previous exploration work led to a global historic resource topping 500 million tonnes within widespread, stratiform clay-rich horizons or beds known as mantos. Up to seven mantos have been identified, and are dominantly oxides, with minor sulphide mineralization.

Baja Mining’s current focus is to convert enough resources to the measured and indicated category for a 20-year operation, with at least 40% being measured resources for the first 12 years in order to secure production financing.

The company has retained prominent metallurgical and engineering firms to address other aspects of the proposed mine, and has also completed mine trial tests at the project to guide design of a safe, full-scale underground mine capable of producing more than 2.5 million tonnes per year.

While previous operators had examined an open-pit mining scenario, Baja believes that the most appropriate method for mining the clay mantos and breccias would employ underground room-and-pillar techniques with pillar removal similar to that used by the coal industry in North America, Australia and South Africa.

Metallurgy has also been a challenging proposition at Boleo, particularly during periods of historic low metal prices, but recent technological breakthroughs offer potential for much improved recoveries of a broader range of metals and minerals than in the past.

The feasibility study will focus on a number of key areas, including leaching of metal sulphides and oxides for maximum metal extraction into solution, the need to use seawater for leaching (fresh water is not available at the site), and difficult solid/liquid separation and washing because of the ore’s high clay content. Other areas to be addressed include the recovery of copper from complex solution containing chloride from seawater, the recovery and separation of cobalt and zinc from a complex solution including high levels of manganese, acid consumption, and manganese recovery as a byproduct.