Warren Rehn
President and CEO
Golden Minerals Company
View from the Top

New Tech Helps Close Cost Gaps and Enhance Gold Recoveries

By Lorenzo Núñez | Tue, 07/13/2021 - 10:16

Q: What results did you obtain from using the BIOX technology at the Velardeña project?

A: The Velardeña project is a poly-metallic gold and silver vein deposit, meaning it produces lead, zinc and values of gold and silver. Using BIOX technology means we do not need to sell the pyrite concentrate directly to the smelters. It gives us the opportunity to oxidize the pyrite and arsenopyrite artificially, using sulfur-metabolizing bacteria. Once it is oxidized, we process that material at our cyanide plant at Velardeña, where we extract the gold and start pouring gold bars. With BIOX, we get 90 percent payable recovery of the material compared to the 20 to 30 percent that we were obtaining previously. 


Q: What is the process for embracing new technologies such as BIOX to make operations more efficient?

A: There are no active bio-oxidation facilities for precious metals in North America, although there have been a few trial plants, including one plant in particular that was located in Nevada and was not successful. Unfortunately, the failure of that particular operation led to a general mistrust regarding the technology, which is in my opinion completely unjustified. This technology is operating successfully in Africa and Australia, under conditions that are essentially identical to the conditions in Mexico or the Southwest US. It has just been a very slow process to get the mining community to re-engage with this technology. The advantage of bio-oxidation as opposed to pressure oxidation is the much lower capital cost of the equipment. For pressure oxidation, you are essentially building giant pressure cookers, which have a much higher engineering and construction cost. Bio-oxidation involves stainless-steel tanks that use atmospheric pressure.

We are looking forward to introducing the first bio-oxidation plant in Mexico and North America. I think there is a great opportunity for similar, smaller mines that perhaps are unable to afford the high capital cost of pressure oxidation and would consider using a bio-oxidation process, which is a tenth of the capital cost or less for a pressure oxidation facility of similar size.


Q: How has the Rodeo project evolved after the incorporation of the second regrinding mill?

A: We are excited because it has been a very smooth startup. Now that we have the additional milling capacity installed at the mill, which was done in April, we have been able to ramp up from our initial 200 tonnes per day to what we had predicted would be about 450 tonnes per day.  Currently, we are running about 500 tonnes per day through the mill. It is a very high-grade gold mine at about 3.3 grams per tonne of gold. For an open pit, that is quite a nice grade. We are also getting very good recoveries from the materials.


Q: How will the Rodeo project support the company on its road to success?

A: This was the most important project for the company this year because it allowed us to transform from being solely an exploration company to being a profitable producing company. The Rodeo mine gave us a unique opportunity at a very low capital cost of about a US$1 million pre-production investment to get up and running and transform the company into a profitable business at very low risk. This project was key to our transformation, and I cannot stress enough how important it was to have the cooperation of the permitting agencies in Durango and the infrastructure available to us.


Q: How is Golden Minerals incorporating ESG at Rodeo?

A: We go through all the steps to get the environmental permissions required and we have really focused on making sure we meet all requirements to get that process underway. With regard to sustainability, we would very much like to be able to continue beyond the initial two-and-a-half-year life span of the mine. Today, we are considered an important employer in the Rodeo area. Some of these rural areas in Mexico do not have many opportunities for employment and this is why it is important for us to maintain a good relationship with the community. In the case of Rodeo, we are on a private ranch and we have a good working relationship with both the ranch owner and the surrounding community. We put a lot of effort into making sure that our communication is open, with very transparent disclosures to the parties involved in the permitting and sustaining processes of the mining operation.


Q: What opportunities do you see for the Yoquivo project and the Santa Maria project through Fabled Silver Gold Corp.’s acquisition of this property?

A: We are dedicated to continue growing the business through exploration with new assets, as well as looking to expand existing assets. We are excited about the Yoquivo project. It is a historically producing district in Chihuahua, where we had encouraging initial results that we published in January.  We are planning to start another phase of exploration drilling to understand what the resource potential is. Santa Maria is very close to Parral and it has been a historic producer as well. Right now, Fabled Silver is doing great work in trying to expand on that resource and start potential production. 


Golden Minerals Company is a Colorado-based gold-silver producer, with one mine operating in Durango State, Mexico and a portfolio of precious metals exploration and development projects in Mexico, Argentina and Nevada.

Lorenzo Núñez Lorenzo Núñez Junior Journalist & Industry Analyst