Science of a Reactive Ore Body
Tom Boerner is a land owner in Menominee County, Michigan, including property in close proximity to the Aquila Resources Back Forty Project. Aquila Resources is a junior mining company based out of Canada, and is in the developmental stage of a zinc/copper metallic sulfide ore deposit adjacent to the Menominee River. Shakey Lakes County Park, Shakey Lakes Savanna (an area of documented endangered and threatened species), and archeological remnants of an extensive Native American village, all occur very close to or within the proposed mine site.
Tom was a member of the 632 mining work group, which drafted Michigan's current non-ferrous metallic mining law and regulations. Tom is not ‘anti-mining,” but is against the pollution by metallic sulfide ores that cause irreparable damage to the environment. Tom is also concerned that laws he thought he was helping to write were later modified in favor of mining interests.
It's important to convey from a scientific basis why mining metallic sulfide rock along the Menominee River would be disastrous. First, there has NEVER been a mine of this type anywhere in the world that hasn’t caused significant environmental damage.
The main cause of any mining pollution is through chemical reactions. In this particular ore body, we need to worry about the formation of sulfuric acid (which is the same as battery acid). A simple Google web search for Acid Mine Drainage should shock anyone. It’s that bad! Once acid mine drainage forms it can not be stopped.
Sixty Islands - Menominee River photo Doug Cornett
I helped write the new Michigan law. I was disappointed that it was changed, after all our “consensus” negotiations, in favor of mining interests.
Steve Hoffman of the US Environmental Protection Agency (EPA) wrote in his report “Mine Drainage Prediction” that pollution from mines of this type are the single largest pollution liability facing the United States today.
Acid mine drainage is formed by a series of complex geo-chemical and microbial reactions that occur when moisture and oxygen come in contact with a reactive ore. In this case the reactive ore is sulfide-based.
How much ore? That number keeps growing. According to Aquila Resources, the deposit appears to be at least 7,000,000 tons. Regardless of how big it gets we’re talking tens of billions of pounds of material. This ore isn’t pure. There may only be a few ounces of desired metals per ton of the mined rock.
This deposit is touted as being a zinc/gold deposit but it also contains other heavy metals that are known to be toxic, cause birth defects and retard mental development in children.
Acid Mine Drainage in Sudbury, Ontario photo courtesy Save the Wild UP
If allowed to be processed here in the Upper Peninsula, the problems then are compounded exponentially. If only a small percentage of this ore is valuable and there are billions of pounds of it, there will be billions of pounds of waste material left behind. This ore could be processed at the Humboldt Processing Facility, owned by Mineral Processing Corporation, a partner in this mining venture. The plant is located on the Escanaba River in Marquette County, north of the current mine location.
Why isn’t the rock found there now polluting the environment?
In physics, the smaller the particle is, the greater the surface area, and the greater potential for reactions. “Surface area” of a particle is defined as the sum of the exposed sides of the particle. Remember Science 101? When looking under a microscope, table salt (NaCL) looks square. There aren’t any nooks and crannies in its form. This shape equates to a low surface area.
Other more reactive particles have a high surface area. An example of how smaller particles react fast are the hand warmers packets we use when hunting. These contain iron filings, and enough moisture and air, so that when the packet is squeezed there is a reaction that produces heat. This is simply an exothermic reaction (rapid rusting) which generates the heat.
If we were to grind the iron in the hand warmers even finer and mix it with fine ground aluminum, the highly reactive surface area would have a very fast and violent exchange of ions (this is called the Thermit process), generating up to 4500 degrees F of heat. This is enough heat to weld railroad tracks together in just a few seconds.
Then how does surface area impact this mine? In multiple ways. Presently the surface area of the ore body is very low since it is now in the form of solid rock. There is now little oxygen in this billion year old rock, so that now any reactions that may be occurring aren’t very significant.
Since it’s impossible to remove the ore from the ground as one large particle, it needs to be broken down. A mining company will use explosives and machinery to break down the one big rock into many billions of smaller ones. By crushing the rock, the surface area, and also potential reactivity, would be multiplied by a factor of many trillions. Just a single gram (1/28 of an ounce)of zinc dust has a surface area of between 1 and 150 square yards, when all the nooks and crannies are unfolded! One ounce, when “unfolded” would cover an area larger than an acre!
Remember, we’re talking about billion of pounds of crushed ore. My calculator doesn’t go that many zeros out, but the surface area of this much material would be greater than the surface area of the earth. Now THAT is potential for reactivity!
Mining operations of this type routinely crush the ore to a particle size comparable to talcum powder. This is done to increase surface area, so the reactivity with cyanide (or other chemical reagent) is greater. Did I mention cyanide? Yes, this is often part of removing gold (heap leaching) from the ore. How much cyanide? Lots of ore means hundreds of thousands of tons! I’ll save that for another day…
Even without reactions (a physical impossibility) mining adversely impacts our water table. Any mine needs to “dewater” the area it occupies, because mining typically creates holes in the water table. Filling the mine with water isn’t acceptable so wells are placed around the mine site to suck out water. Pumps are kept running to prevent the mine from flooding. Thus the surrounding water table is lowered.
This “dewatering” will most likely impact the aquifer (Shakey River, Shakey Lakes, Menominee River, creeks, springs, wells, swamps, etc.) for many square miles and affecting thousands of acres of wetlands. In addition, processing the ore could use approximately 3000-gallons per ton of rock. This equates to using billions of gallons of water. My rough estimate of processing an ore body of 10 million tons could use enough water to cover 1,380 acres with water 100-feet deep. Whose water is it? Ours and our children’s - that’s who!
With a mine such as the Back Forty, there are major issues that can not be overcome in order to stop pollution - the high surface area of a highly reactive ore, a moist environment that promotes both chemical and biological reactions (humidity, snow, rain and groundwater), and the high potential for the mix of this to result in acid mine drainage.
Our water is too precious. Mining sulfide rock right next to the Menominee River is a very bad idea!