March 1, 2012 by Hematite
Proponents of the proposed iron mine in the Penokees claim that there are two kinds of rock: overburden waste rock (the Tyler shale) and iron ore. To date, the main concern with the Tyler is the presence of sulfide in the form of pyrite, or iron sulfide. When disturbed by mining and exposed to air and water, pyrite oxidizes to produce sulfuric acid, which is toxic and would cause serious environmental damage to the Bad River watershed and the Kakagen Slough. Two weeks ago we presented results of a compositional analysis of a sample of the Tyler shale. Our sample contains a substantial amount of pyrite, confirming the results of previous studies and other workers.
After re-examining our data, we now know that the distinction between waste rock and ore is false. Both rocks are potential ores. The Tyler contains not only sulfide, but also economically minable phosphate in the form of apatite, or calcium phosphate. The phosphate content of our sample ranges from 5 to 10%. There is no reason to suppose that our sample is unusual. Phosphate is not homogenously distributed, and in places may be as high as 20% or more. Phosphate has been reported from the Tyler and from contemporaneous black shales in Michigan and Minnesota.
Iron mining in the Penokees likely will result in large areas of land being covered with crushed, phosphate-rich rock. If significant amounts of this phosphate enter the bad river, the results could be massive algal blooms that cutoff sunlight and deplete oxygen in water. The ecological consequences of phosphate pollution are severe and well documented. Anyone familiar with the great bowls of pea soup Madison lakes become in the summer knows exactly what phosphate can do to bodies of water. Additionally, phosphate runoff is responsible for large “dead zones” in the Gulf of Mexico, and has polluted parts of the Mississippi River.
At this point, we can only speculate about whether Gogebic Taconite (GTac) is aware of phosphate ore in waste rock overburden, but there are important consequences to this new information about phosphate in the Tyler shale. While the United States is awash with cheap iron ore, it is facing a critical shortage of phosphate, which makes phosphate mining potentially far more profitable than iron mining. In the search for new sources of phosphate attention will turn to the Tyler shale.
From the 1950s through the 1970s the US Steel Corporation took over 200 core samples of the iron deposits in the Penokees. Many of these cores include parts of the Tyler Formation. These cores currently are in the possession of RGGS Land and Minerals of Texas, the company that now owns mineral rights in the Penokees and is leasing them to GTac. Many questions about the Tyler could be answered by examining these cores. To date, RGGS has refused give the public access to them. Whether GTAC has seen the cores, and how much information GTAC has on the composition of the Tyler, is not clear.
What is clear is that detailed information about the composition of the Tyler should have been available to legislators and the public long ago. That fact the presence of phosphate in the Tyler is only now coming to light, on the eve of the final legislative debates over mining, is a mark of how little science has actually been considered in the drafting and discussion of a “scientific” mining bill. And the fact that media coverage of the mining bill has included almost nothing about the scientific issues involved shows how ill prepared the Wisconsin press is to competently report on the mining issue.
To repeat: the distinction between waste rock overburden and iron ore is false. Both rock are types of ore. If AB 426 passes GTac or another company could open an iron mine but make its real money on phosphate. In any case, any mine in the Penokees will expose to the Bad River watershed to the effects of both sulfate and phosphate pollution.