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Rare Earth Elements in U.S. Not So Rare

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The USGS has just released the first-ever nationwide assessment of rare earth elements in the United States. The report estimates total U.S. resources at just under 12 million metric tons, located in significant deposits in 14 states. Keith Long and Brad Van Gosen, the two lead authors of the report, discuss their findings.




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Alex Demas:  Hello and welcome to this edition of the USGS CoreCast. I'm your host Alex Demas. Today we'll be discussing a newly released report that documents the first ever nationwide assessment of rare earth elements within the United States. Rare earth elements are important parts in the high strength magnets, metal alloys for batteries and other essential components for electrical vehicles, photovoltaic cells, wind power and several key defense applications.

Joining me to discuss this report are the report's lead authors, Keith Long and Brad Van Gosen. Keith, Brad thanks for joining me. So Keith why was this study done? Were we asked to do this? Or did we decide to do this on our own?

Keith Long:  We were asked by the Department of Defense to prepare a summary of what is known about our domestic resources or rare earth elements and this is something we've been working on for some time but there's an urgent national need to address the issue of the adequacy of supply of rare earth elements so the Department of Defense was asked by congress to do a study on the supply of rare earths in the United States and deal's is not only with rare earths as their mine and processed but also in various intermediate products, as well as final consumer such as rare earth element batteries and the like.

01:09And so the Department of Defense went to it much broader than we did. We were just one component where we're addressing domestic resources.

Alex Demas:  So Brad why are they called rare earths exactly?

Brad Van Gosen:  Most of the rare earth elements as not as rare as their group name would suggest they are. They were named rare earth elements when they were identified back in the 18th and 19th centuries because they seem to be relatively rare at that time occurring and some relatively are rare and unusual minerals. In fact Cerium is the most abundant rare earth element and it's actually more common in the earth's crust than copper or lead is.

However, while we now recognize using model and analytical techniques that rare earth elements can occur and small concentrations throughout the earth's crust. It's very unusual to have them occur in concentrated or deposits. They're very rarely occur as what would be considered an economic or a body even though they are fairly common on an average content throughout the earth's crust.02:12Alex Demas:  So why did mining shut down in the United States?

Keith Long:  Well we've only had one significant rare earth producer and that was Mountain Pass in California, which is now in the process of reopening. But the reason that the company who'd own it made a decision to shut down, you know, I can't speak to that.

Alex Demas:  Why hasn't the US reopened its mines.

Keith Long:  Well it's again a matter that each company involved would have to addressed because it deals with the economics of a particular deposit. 

Alex Demas:  What exactly are rare earth resources? We have on our website that we have 13 million tons of rare earth reserves but your report speaks in terms of 13 million tons of rare earth's resources. Could you explain the difference?

Keith Long:  Resources are concentrations of rare earths that are potentially economic to mine but in order to be classified as a reserve, it had to be demonstrated that it's economic or resource. 03:12And the standards for what can be classified as a reserve of considerably tighter over the recent years and so a lot of our older numbers particularly with rare earth are somewhat out of date with only things reserves that today we'd legally called the resource. So in this study we kind of corrected that but the important thing to realize is that even though the standards of what can be legally called a reserve are very strict and for that reason, only one deposit in the United States has a legally defined reserve that would be in Mountain Pass in California, its that the resources we have identified are tomorrow's reserves. So most people for the work on it as they're doing exploration work today  in Bokan Mountain in Alaska and Bear Lodge in Wyoming. At least part of those resources will eventually be upgraded into a reserve.04:01That is will be demonstrated that can be economic to mine.

Alex Demas:  On table table ten of your report where you're showing the overall tonnage of the various deposits, you have several different columns. The first column says tonnage and the next column says contained tonnage and in the middle you have something about grade, could you explain a little bit about how that whole process works?

Keith Long:  Yes. We don't find rare earth in the pure form in nature. What we do is we find them in low concentrations within rocks generally with rare earth minerals the total rare earth content of something you would mine will be somewhere between 2% and 8%. And so the way we evaluate these resources is we'd like to know what the concentration level is because that has a lot of bearing on the economics of mining. The higher that great number is, the more economic usually it is. 

So we generally, when we lift our data with respect to reserves and resources, we typically show a column showing a total tonnage of mineralized material, then we have another showing the concentration of rare earth on that material, that is the grade. There'll be another column where we just calculate what is the total tonnage a rare earth contained in the tonnage of mineralized material.05:15Alex Demas:  So Brad, where are rare earths typically found?

Brad Van Gosen:  Well there are few geologic environments. The largest type of host for the very largest rare deposits are in unusual igneous intrusion called carbonatites. These are calcium and magnesium rich igneous bodies and also tend to be less enriched in silica in comparison to a normal igneous rock such as your typical granite. These large carbonate-rich intrusions are called carbonatites and they're fairly unusual across the world. The largest carbonatites containing what we think are the largest concentrations of rare elements are the prime noble carbonatite in China, in Mongolia and the Mountain Pass deposit in Southeastern California, not far Southeast of Death Valley in west of Las Vegas.06:20And these calcium-magnesium rich igneous masses can contain up to several percent rare earth elements. In fact the Mountain Pass deposit reportedly has roughly 9% rare earth element oxide content. Other types of deposits are vein deposits again associated with unusual intrusions of alkaline igneous rocks that is again less silica than a normal such as a granite and enriched in not only in magnesium and calcium but also sodium and potassium. And we have examples of these vein-type deposits up at Bokan Mountain on the south and the Prince of Wales island and southernmost Alaska. 07:07We have examples in the Bear Lodge Mountains, up in northeastern Wyoming. And these vein deposits can contain several percent in our rare earth element oxide. Another type of deposit that can contain concentrations of the rare earth element-bearing minerals are plasters. These are simply sand deposited by rivers, streams and then we have examples of these in Idaho, North and South Carolina and then beaches of Georgia and Florida.

And then finally, we have another unusual example of some types of iron deposits that can be associated with these alkaline igneous fanners and we have examples of magnetite-hematite iron deposits at Pea Ridge in eastern Missouri and then in the mine-built district in upstate New York just west of Lake Champlain.08:01And some of these iron deposits can contain unusual concentrations of the rare earth element.

Alex Demas:  Keith, where does the US fall overall in rare earth resources?

Keith Long:  Well generally the United States is thought to have about 15% of known world resources of rare earth elements. But China has a much larger share but other countries like Australia and Canada have significant shares as well. So we can take that China is the leader when it comes to known resources and then there's the secondary countries like United States, Australia and Canada that have very significant resources. Now bear in mind that the market for rare earth is rather small relative to the size of these resources, there's considerable room for the United States to meet its own needs as well as some other countries as well.

Alex Demas:  Brad, Keith, thank you very much for joining me.

Keith Long:  You're welcome.

Alex Demas:  This CoreCast has been a product of the US Geological Survey Department of the Interior. For more information on this CoreCast and other CoreCasts, please visit our website at Thank you for joining us.

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