Published on June 20, 2018
Midas Gold Idaho wants to keep the community informed about the work we are doing at the Stibnite Gold Project site. The Ask Midas blog series gives the experts in our company a chance to answer some of the community’s most frequently asked questions and help clear up any misconceptions around the project.
Miners have relied on cyanide to extract gold and silver from ore for more than 100 years. Throughout this period of time, we’ve learned a lot about how to use this chemical in a way that is safe for both humans and the environment and we will implement these advances at the Stibnite Gold Project. Although cyanide can be toxic in high concentrations, we have a plan to use it safely and without any harm to the environment, wildlife or our employees, just as many operating mines across the U.S. currently do. Let me explain how.
IS IT SAFE TO USE CYANIDE AT THE STIBNITE GOLD PROJECT SITE?
Cyanide is a naturally occurring compound made up of carbon and nitrogen; elements that are common in nature and abundant in our own bodies. Like any compound or chemical, including salt, soap or ammonia, cyanide can be toxic at high concentrations. However, like other chemicals, low concentrations of cyanide are useful. Cyanide is present in many of the products we use each day and is found in the foods we eat. It is added as a stabilizer in table salt and occurs naturally in the pits of apples, plums and apricots. Cyanide is also incredibly helpful for processing gold.
At the Stibnite Gold Project, we will use a weak sodium cyanide solution to extract gold from the ore we mine. Cyanide has a natural tendency to bond with metals, even when they occur in microscopic amounts, such as gold and silver in ore. This method of gold recovery has been popular for over a century. Advances in technology have allowed companies to use less and less of cyanide to achieve similar results.
At our project, we will meet or exceed all of the standards of the International Cyanide Management Code, which was developed and adopted by the industry after incidents at mines in Eastern Europe and South America. Idaho’s Department of Environmental Quality will also have to review and approve all of our plans for cyanide use at our site.
At Stibnite, to make sure we are doing things in the safest way possible, all gold ore processing will happen inside an enclosed facility in order to protect the environment. Our building will have 110% containment for all solutions being used. We will use as little cyanide as possible at the site, which will not be difficult since cyanide works so well for gold recovery and is not needed in large amounts or high concentrations. After the ore is mined and crushed, it will be placed in large tanks and mixed with a dilute sodium cyanide solution that contains less than one percent of cyanide. This process extracts the gold from the ore and allows us to recover it to make mixed gold-silver doré bars for further processing off-site.
One of the processes that really sets our use of cyanide apart from operations in the past is the water, cyanide, ore mixture will be chemically treated using a cyanide destruction process, located within the processing building, before being placed in our fully lined tailings storage facility. This process reduces the levels of cyanide to negligible amounts before it ever leaves the contained building. Neutralizing the cyanide is an imperative step in our process to meet our own needs. We plan to recycle water from our tailings storage facility and reuse it in a part of the gold production process, the flotation circuit, where cyanide is not supposed to be present. If any measurable levels of cyanide remain in the recycled water, it would negatively impact gold recovery in flotation.
As we’ve developed our plan for the Stibnite Gold Project, we have given a lot of thought as to how we can minimize our impact on the environment and have put many safety measures in place. We feel confident that our cyanide use will be safe and ultimately be the most responsible way to recover gold at the site.
If you have a question you would like us to answer, please email it to [email protected].
