Published: August 4, 2021 |

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Trevali Mining said a pilot plant testing program using Caribou run-of-mine and milled material at FLSmidth’s Rapid Oxidative Leach (ROL) process testing facility in Salt Lake City, Utah, is underway. The program expands on previous laboratory test work and is aimed at demonstrating the potential to recover zinc, lead, copper, gold, and silver as a precipitate or metal and additional zinc and lead from Caribou ore and mill tailings.

If the pilot plant testing program indicates that the ROL technology has the potential to be successfully implemented at Caribou, it may allow Trevali to replace the existing flotation circuit at Caribou Mine with atmospheric leach vessels and potentially an SX/EW train, introducing the possibility of producing base and precious metals on-site and thereby save transport costs and offsite treatment costs.

Highlights:
• Leach test program targets an improvement to zinc, lead, copper, gold, and silver metal recoveries.
• Potential to produce a precipitate or metal on site replacing the current ore concentrate that is produced at
  Caribou, which, if implemented, would lead to savings on transport costs and offsite treatment costs.
• Opportunity to process historic mill tailings, which include gold and copper metals, in addition to run of mine
  ore, increasing revenues and reducing closure liabilities.
• Potential to reduce Trevali’s carbon footprint at Caribou.
• Potential to extend Caribou’s mine life and treat lower-grade deposits in the Bathurst camp.
• A successful pilot plant test program is expected to support future study work on a preliminary economic
  assessment and NI-43-101 technical report which includes potential processing of the Trevali mill feed
  and mill tailings and production of metal on site.

The initiative is consistent with Trevali’s strategy to extend the two-year mine plan and investigate further longer-term value-enhancing opportunities in the Bathurst Mining Camp. In addition, the technology has the potential to reduce the company’s carbon footprint and provide other sustainable environmental benefits via the re-treatment and disposal of tailings.

Conceptual Objectives of the Program Include:
• Recovery of metals/minerals that are not recoverable utilizing the current technology at Caribou (precious
  metals and magnetite)
• Improved payables/selectivity of the traditional flotation process utilizing new and emerging technologies

“FLSmidth’s Rapid Oxidative Leach metallurgical technology has the potential to transform the Caribou mine and the wider Bathurst Mining Camp. If viable at Caribou, the technology may increase metallurgical recoveries, produce precipitate or metal on site, including copper and gold, and reduce or eliminate freight costs and treatment charges related to concentrate,” said Ricus Grimbeek, president and chief executive officer of Trevali.

“This next phase of the testing program is an essential step in evaluating the suitability and economic viability of a processing solution with the potential to enhance the value of the in-situ material and tailings at Caribou as well as the surrounding deposits in the Bathurst region. The positive results to date support further study and analysis given the potential implications for the Bathurst Mining Camp in general and Trevali in particular,” added Grimbeek.

Beyond quantifying the ability to recover additional metal values, the objective for the pilot plant test program is to determine the various kinetic factors, mass and energy balance, and engineering data to support future engineering on a preliminary economic assessment for potential processing of the Trevali mill feed and mill tailings and produce metal on site. Continuous pilot plant trials commenced in June 2021 (Phase 1) to tune the pilot plant and provide material for precious metal leach tests in late July, followed by a test program at the Caribou Mine site that is planned for September 2021 (Phase 2). Leach data and results are expected to verify that batch testing results can be achieved in a continuous operation.

Process Description

FLSmidth’s patent-pending ROL process utilizes a stirred media reactor to achieve improved metal recoveries under atmospheric conditions within a reasonable amount of time. This mechano-chemical approach overcomes many of the surface passivation problems that have hindered other atmospheric leach processes. The process takes advantage of the enhanced reactivity of transitory, surface-defect structures generated during particle fracture. The process occurs at 80-90 °C and under atmospheric pressure. The use of very low energy, inter-stage attrition/grinding is used to enhance the selective dissolution of valuable minerals.

Rapid Oxidative Leach Benefits:
• Avoids the excessive production of sulphuric acid.
• Lowers the carbon footprint by reducing shipping volume.
• The process is scalable.
• Mechano-chemical stirred media reactors (SMRt) perform the mechanical surface activation.

A Path Forward

Trevali has a foothold in the Bathurst Mining Camp, which is a valuable and important mining region to New Brunswick and Canada. Infrastructure, mining innovations, economic impact, social effects, and environmental initiatives comprise a few of the reasons for the camp’s continuing importance. Since 2000, mine closure and reclamation have outpaced mine development in the Bathurst Mining Camp. Although at a very early study stage, applying FLSmidth’s ROL technology at Caribou may provide an opportunity to begin a reversion of that trend in an environmentally friendly and sustainable manner.

About Trevali
Trevali is a global base-metals mining company headquartered in Vancouver, Canada. The bulk of Trevali’s revenue is generated from base-metals mining at its four operational assets: the 90 percent owned Perkoa Mine in Burkina Faso, the 90 percent owned Rosh Pinah Mine in Namibia, the wholly-owned Caribou Mine in northern New Brunswick, Canada, and the wholly-owned Santander Mine in Peru. In addition, Trevali owns the Halfmile and Stratmat Properties and the Restigouche Deposit in New Brunswick, Canada, and the past-producing Ruttan Mine in northern Manitoba, Canada. Trevali also owns an effective 44 percent interest in the Gergarub Project in Namibia, as well as an option to acquire a 100 percent interest in the Heath Steele deposit located in New Brunswick, Canada.

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