Tag Archives: BIOX

Corvus Gold weighs heap leach, BIOX route at Mother Lode project

Metallurgy, Mineral processing, Mineral project development, Mining equipment, Mining project news, Precious metals, , , , , , , , , , ,

Corvus Gold has announced the results of a preliminary economic assessment (PEA) for its Mother Lode project (MLP) in southwest Nevada, USA.

The study outlines a project able to produce 170,980 oz/y of gold and 79,600 oz/y of silver through a combination of heap leaching and biological oxidation (BIOX).

Based off measured and indicated resources of 1.55 Moz of gold and 1.51 Moz of silver, and inferred resources of 170,000 oz of gold and 400,000 oz of silver, the study estimated an operation with an eight-year mine life and an initial price tag of $406 million. Using a $1,500/oz gold price, the payback period was estimated at 2.7 years.

Jeffrey Pontius, President and CEO of Corvus, said: “The results from our initial PEA study of the Mother Lode standalone project are encouraging. The potential projected annual gold production of over 200,000 oz/y during the first three years is significant, especially as a new project, which could provide an increase to the Corvus Gold future production profile. The PEA demonstrates the preliminary potential for the project, on its own, to produce significant free cash flow and after-tax NPV.

“Corvus now has a number of strategic alternatives available to it to drive shareholder value. Given the recent interest in the Bullfrog Gold District from multiple producing companies with adjacent land packages, Corvus’ compelling and accretive projects and its commanding land position with what we believe is demonstrated high exploration potential, has positioned the company to deliver increased shareholder value.”

The Mother Lode project is modelled as a large, open pit, with a biological oxidation mill to treat the higher-grade sulphide mineralisation and a heap leach pad for treatment of oxide mineralisation. The mining plan uses standard mining practices and has a production scale that is currently being used by many operating mines, the company said.

The new PEA study, which assumes a standalone project, also includes a number of other changes to the previously assumed concept for the combined Mother Lode-North Bullfrog project configuration, which enhance the project. This includes:

  • Employing BIOX to treat the MLP sulphide mineralisation would increase gold recovery by 11%. Metallurgical testing of a stirred BIOX process on the MLP whole sulphide mineralisation from Mother Lode demonstrated gold recoveries of 91-92% as compared with the previous testing on MLP flotation concentrate;
  • Eliminating the need for the concentrator, oxygen plant and autoclave components of the previous plant concept simplified the plant conceptual design and would reduce the process plant capital cost;
  • Ongoing work expanding Mother Lode resources in the CIZ area and the main Zone with ongoing work at improving the open-pit mining and development plans will enhance project economics; and
  • New experimental work on conducting the BIOX process in a heap is being tested as follow-up on past successful studies and could substantially cut operation and capital costs with the elimination of the mill circuit.

The PEA only includes drill results completed up until September 2020. In addition, Corvus will continue follow-up mineral resource expansion work and new discovery drilling on priority targets at both the North Bullfrog and Mother Lode properties through 2021, it said.

Outotec addresses cyanide consumption with new BIOX refractory gold process

Environmental, Metallurgy, Mineral processing, Precious metals, Sustainable mining, , , , , , ,

Outotec has introduced its new MesoTHERM BIOX process to significantly reduce cyanide consumption in refractory gold ore treatment.

Traditionally, cyanide consumption with conventional bio-oxidation residues is higher than with residues produced through other oxidative technologies. The Outotec MesoTHERM BIOX® process, based on Outotec’s existing mesophile BIOX process, offers an easy, cost-effective upgrade path that can cut cyanide consumption by as much as 50% compared with conventional bio-oxidation, the company claims.

The BIOX process, which has been in commercial operation for over 30 years, was developed for the pre-treatment of refractory concentrates ahead of conventional cyanide leaching for gold recovery.

“The Outotec MesoTHERM BIOX process enhances the established mesophile BIOX process by combining mesophile bio-oxidation technology with a higher-temperature thermophile oxidative stage to enable an even more effective overall sulphide oxidation step,” Outotec says.

On top of cutting cyanide consumption by as much as 50% compared with conventional bio-oxidation, MesoTHERM BIOX significantly reduces the formation of thiocyanate – a common and stable cyanide species traditionally formed as a further by-product, the company said.

Solubilised species prevalent in the mesophile stage are decanted off in an inter-stage thickening step between the two oxidative processes, simplifying operation of the thermophile stage, the company explained.

For existing BIOX customers, upgrading to BIOX MesoTHERM is a “relatively simple process”, Outotec says. It involves reconfiguring the circuit with the addition of Outotec’s High Rate Thickeners for inter-stage thickening and Outotec OKTOP® Atmospheric Reactors for the thermophile step.

Craig van Buuren, Senior Process Engineer, Outotec, said: “Our conventional mesophile BIOX process has enabled the production of over 25 Moz of gold to date. This novel process takes advantage of these proven technologies to help our customers achieve significant cost savings while also reducing their environmental footprint.”