How Maelgwyn’s “Golden Bubbles” Leachox Refractory Gold Process Contributed to the Addition of over One Billion Dollars to the Bottom Line of One of the World’s Best Mining Companies.

It’s not often that one can praise the foresight and management of a gold mining company when it comes to innovation and new technology introduction, especially in the area of mineral processing. Normally, as is our experience, most are very blinkered to such concepts and tend to focus on promotion activities in an effort to raise the company share price, rather than on actual operations and activities like increasing production and reducing costs and looking after the various stakeholders’ interests.

So, it was refreshing to find a mining company that thought out of the box. To its eternal benefit Maelgwyn found such a company back in 2009 and it will be of no surprise to anyone involved in mining to hear that the company was Africa focused gold mining company Randgold Resources.

Randgold, with its leader, CEO Mark Bristow was the darling of the mining industry for a decade until its merger with and into Barrick Gold Corporation in 2019.  Mr Bristow now leads the new Barrick into the future and has taken the best practices established at Randgold with him.

Randgold was recognised as being at the forefront of environmental, social and governance (ESG) issues way before it became fashionable in the mining industry. Its support to countries, the environment and the local population where it operates has been exemplary.  It’s advanced practices’ in exploration geology and mine planning are well known in the industry.  But less well known is its embracement of new technology and concepts in the way gold ore is processed.

It all started back in 2009.  Randgold were already operating a number of gold mines in Africa and had discovered or acquired what would become world class gold deposits at Tongon in the Ivory Coast and Kibali in the Democratic Republic of Congo.  The problem with these deposits, like most in west and central Africa, was that they had refractory components to some degree. This made the processing of such ores for gold recovery difficult by conventional means or requiring very high capital cost associated with advanced processing methods of pressure oxidation or bacterial leaching.

By this time Maelgwyn had developed and patented world-wide its Leachox process;

“Extraction Process for Metals like Gold and Platinum including Fine Grinding, Pulping and Oxygenating”

The process involves the also patented Maelgwyn Aachen Reactor combined with ultra-fine grinding and the leaching of concentrates.  Maelgwyn had previous success with the process at a number of gold operations treating refractory gold ore and Randgold wanted to investigate the technology and processes.  So, it installed a number of Aachen Reactors at its existing Loulo gold operation in Mali, essentially to undertake due diligence on the technology.  Loulo ore was not particularly refractory but the Aachen Reactors immediately and dramatically increased the dissolved oxygen levels in the process (required for gold leaching), reduced reagent consumption and importantly increased gold recovery.  We made this amateur “home movie” at the time of the Loulo operation. It’s not the most riveting movie but of interest near the end of the film is the jump in dissolved oxygen levels in the leach tanks from below 2ppm to 28ppm when the Reactor was put on-line.

 https://youtu.be/KfYehwOJvEo

After months of operation of the Aachen Reactors to prove reliability Randgold was convinced of the process and worked with Maelgwyn and its metallurgical laboratories to come up with a workable process concept for its Tongon and Kibali projects. Both process plants for these projects were designed around the Leachox process. 

Kibali is considered one of the “Tier One” gold operation in the world producing nearly a million ounces of gold annually. As with most gold ore deposits Kibali consisted of a covering of weathered oxide ore, underlaid be a layer of transition ore. Essentially transition ore is a mix of weathered and primary un-weathered ore or any combination in between. Not necessarily a major component of the orebody but difficult to process. Under the transition ore was the primary sulphide ore. This primary ore was the majority of the orebody and refractory in nature.

Randgold designed the process flowsheet for Kibali to first treat the oxide ore by a conventional Carbon in Pulp method with Aachen Reactors installed to increase dissolved oxygen levels, negate cyanide consuming species in the ore and maintain a higher level of gold recovery. When transition ore was introduced the Reactors had to work harder to maintain maximum recovery.  However, the plant was designed to be able to treat the majority of the orebody in a separate circuit where the gold was contained in refractory sulphides. To this end a flotation plant and concentrate ultra-fine grind circuit was installed prior to the Aachen Reactors. Combined with ultra-fine grinding the Reactors partially oxidized the sulphides thus liberating gold particles to be leached. The Aachen Reactors also negate passivation to also assist the gold leaching process.  Finally, Aachen Reactors were also installed in combination with the Air/SO2 cyanide destruction process to make the plant tailings safe for depositing in the tailings dam.  In all there were 18 Aachen Reactors installed at Kibali. Eventually Aachen Reactors were installed or retrofitted into all Randgold’s operations.

Mark Bristow, CEO of Randgold and now CEO of Barrick Gold is reputed to have referred to the Leachox process and the Aachen Reactors as the “Golden Bubbles”.  We believe we certainly contributed to the success of Randgold.  We estimate that across all Randgold Resources operations since the Reactors have been installed, they have been responsible for well over one billion dollars in extra revenue for Randgold.  This figure is obviously only a guestimate on our part as most detailed production data of the various mines is confidential. It was estimated on officially released production figures over the time period, results from initial metallurgical testwork and operating plant data where it has been provided to us and then average gold prices. We think this estimate is conservative and does not include the considerable operating cost savings in reduced reagent usage caused by the reactors.

The licence and supply of Aachen Reactors to the client means that they are monitored and maintained by Maelgwyn in a continuous good working order.  This, with the continued support by the Maelgwyn technical team, including metallurgical laboratory development and process trouble-shooting services to the whole operations means that the excellent working partnership between Maelgwyn and Barrick Gold has continued into this next decade.