Thetford Mines industrial test plant – credit, Dundee Sustainable Technologies supplied to the Northern Miner
A Quebec chemical firm has developed a cyanide-free, and generally non-toxic method to extract gold from mineral ores—an option that could potentially relieve companies from a significant portion of current environmental compliance.
The firm, Dundee Sustainable Technologies, also offers a patented chemical process called GlassLock, which addresses one of the industry’s most pressing environmental concerns: arsenic.
The technology can replace cyanide leaching during extraction to isolate the arsenic and turn it into an inert glass. Mixed with common components like silica, recycled glass, and hematite, the arsenic is then vitrified into a stable and insoluble glass product that can be removed and processed far more easily.
Mining companies are not the polluting, Gold Rush-era businesses they used to be. Regardless of where Canadians go around the world to mine, they operate fully-ensconced in the ESG framework of private sector accountability for the ecosystems they work in.
Retreatment of mine waste, pollution control, and reclamation of mining land are costs budgeted for and built into the earliest economic viability assessments of any mining project. Environmental permitting times take anywhere from 8 to 20 years in North America on average while government offices asses any potential harm or risk to air quality, watersheds, and wildlife.
These requirements put enormous risk and burden onto companies looking to supply the market with everything a modern civilization needs to build and produce—from the copper that makes the wires which run through our devices, to the zinc that makes the pipes which bring water through our homes.
In this business environment, Dundee Sustainable Technologies has worked for years from Canada’s strong mining jurisdiction of Quebec to develop cleaner ways to process ores that can both protect the natural ecosystem surrounding mining concessions and relieve the often-small management teams behind mining operations of some of the most stringent regulatory burdens.
Dundee’s gold circuit process uses sodium hypochlorite and sodium hypobromite in ambient pressures and room temperature to extract gold from ore at a fraction of the time of the cyanide-in-leach method. Contact time is short, just 2 hours compared to 36 hours, and the process operates in a fully closed loop. All chemicals are recycled within the circuit for reuse.
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Without cyanide and other toxic leaching reagents, mining plans can be designed without “tailings ponds“—basically small manmade lakes that hold and slowly treat effluent and mine tailings from the milling and leaching process. These themselves aren’t necessarily bad for the environment, unless any number of weather events should disturb them—heavy rain, flooding, an earthquake, or a landslide to name a few.
Already, mining companies are using some of Dundee’s methods. Freegold Ventures Limited, a company formed to develop the Golden Summit project in Alaska, one of the largest undeveloped gold resources in the Americas, has included GlassLock in a suite of metallurgical test work as it prepares a mine plan for the roughly 30 million ounces of gold on its property.
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In tests, Freegold used GlassLock to recover 95% of the gold contained in the ore while isolating 98% of the contained arsenic as inert glass, reducing the toxicity from 7% to 0.17%. It also was able to remove the need for cyanide leaching, and the resulting gold concentrate would be direct-to-smelter quality.
“The results of this program were extremely positive and encouraging for Freegold as it advances the project through Pre-Feasibility,” the company wrote in a press release.
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