Episode 376: US Mineral Dependency

  

Welcome to the History of the Earth podcast where we discuss all things geological. I’m your host, geologist Dick Gibson. There’s been a long hiatus in my production of this podcast, and I hope to rectify that with some new episodes. Today’s topic for Episode 376 is U.S. mineral dependency.

It’s a common misconception, perhaps an expression of “American exceptionalism,” that the United States is self-sufficient in most or all of the mineral commodities we use in our stuff every day. Nothing could be further from the truth.

In my book, What Things Are Made Of, published in 2011, I documented the uses for everything from arsenic to uranium, and where the U.S. gets its supply of each. At that time the U.S. was self-sufficient, a net exporter, of only 19 of the eighty-plus commodities the U.S. Geological Survey tracks. Today, in 2017 the situation is no better – the count is down to 15 items for which the U.S. is a net exporter.

Some of those items are low-value but interesting things like boron, kyanite, and diatomite. Only three, gold, iron ore, and molybdenum, are high-value metals.

A lot of the mineral commodities we import are obscure, but the vast majority of technologically active Americans use them every day. For example, indium, critical to making flat-panel displays for televisions and computers, is all imported, mostly from Canada and China. Zinc is a well-known metal used mostly in galvanizing iron to prevent rust and in brass and bronze for everything from door knobs to saxophones. In the U.S., 82% of it is imported, mostly from Canada and Mexico.

What about that vital bomb-making element, uranium? Hardly any is used to make bombs in the United States any more, but it helps generate electricity in 61 commercial nuclear power plants across the nation, and almost 20% of our electricity comes from nuclear plants. Where does that uranium come from? Only about 4% of it is mined in the United States. The rest is imported, with Canada and Kazakhstan providing close to half, and Russia, Australia, and Namibia supplying most of the rest.

How about something as common as a flashlight battery? Dry-cell batteries are made with zinc, carbon, and a pasty electrolyte of ammonium chloride and manganese dioxide. All the manganese used in the U.S. is imported, with more than two-thirds of the manganese ore we use coming from Gabon in Central Africa. By far most of the nearly 700,000 tons of manganese the U.S. consumes goes to steel alloys, where it helps make the steel resistant to abrasion and stronger in impacts. That makes it a common alloy in bicycle frames and mining tools.

Or consider common salt. Even though there are 64 plants in 16 states, with Kansas leading the way in production, the United States still imports about a quarter of all the salt we use. About half the salt consumed goes to highway deicing, but a third or so is used to make a wide variety of chemicals, including plastics like polyvinyl chloride or PVC. Food processing and common table salt amount to just 3% of the salt used in the U.S. Chile is the largest source for salt imports, with Canada and Mexico second and third.

The point of my book What Things Are Made Of and this brief set of examples is simply to help you recognize the profound level of globalization that exists in everyday products Americans use.

Thanks for listening, and I hope you’ll join us next time for another episode of the History of the Earth. 

—Richard I. Gibson

Episode 375: Garnets

Garnet is the birthstone for January, but there really isn’t a single mineral named ‘garnet.’ It’s a group of at least 15 minerals of differing chemistry, but only six are common. They are three aluminosilicates combined with iron, magnesium, or manganese, and three calcium silicates in combination with either iron, aluminum, or chromium. The definition of a mineral is something with a specific chemistry and a definite crystalline structure.

All six garnet minerals have essentially identical crystal structure. They are in the isometric or cubic crystal system, meaning their three crystal axes are perpendicular and the same length – that’s what isometric means, same length. But garnets seldom form cubes. The molecules are of sizes that result in many-sided forms, including dodecahedrons, with 12 faces, and trapezohedrons with 24 faces, and more complicated shapes, all of which tend to make garnets almost spherical. Often, they look like little soccer balls in the rock.

The word garnet is from an early English word that meant dark red, as many garnets are, but it may ultimately be derived from the words pomum granatum, Latin for pomegranate – because pomegranates have bright red seed covers similar in appearance to common garnets.

And they’re pretty. Red, purple, yellow, brown, orange, bright green for uvarovite, the chromium garnet – and they’re hard, usually around 7 or higher on the Mohs hardness scale. This makes them great for two things: gemstones and abrasives, and they’ve been used for both since the Bronze age.

By far the greatest use of garnets, by volume, is as abrasives. The US uses about 190,000 tons of garnets every year, with about 17% of that mined in New York’s Adirondack Mountains and in Idaho. The rest, 83% in 2014, was imported mostly from Australia and India and a bit from China. India produces about half the world’s industrial garnet, with China second with a third and Australia 15%. The US is a distant fourth with only 2% of world production.

You benefit from garnets every day, even if not directly in the rough surface of an emery board or sandpaper. Waterjet cutting is used to cut and shape metals from steel to aluminum as well as plastics and glass. Besides their use as abrasives, about a fifth of garnet consumption in the United States goes to filtration in water wells.

The value of industrial garnet in the US is about $9 million. Garnets are used for gemstones, but because they are so common, their value is nothing like that of diamonds, sapphires, rubies, and others, most of which are also harder than garnet and much rarer. But garnets can still make beautiful jewelry.

Do I have any garnets in my collection? Yup. Hundreds of thousands of them, but most of them are microscopic, in a rock with a blue mineral called glaucophane from the California Coast Ranges. The biggest one I have is maybe an inch or so across, from Ontario, but at Gore Mountain, New York, there are garnets as much as two feet across in what is possibly the largest garnet deposit in the world. They are in metamorphic rocks related to a continental collision about a billion years ago, called the Grenville Orogeny.

So happy birthday to everyone with a January birthday. Have a garnetiferous day!

—Richard I. Gibson

The Cenozoic Episodes

Running time 3 hours

We are up to the Cenozoic Era in the monthly episodes. This one combines the 31 episodes from December 2014, covering the Cenozoic, into one episode, and it completes the packaging of each month of episodes from the original series.

As usual for this monthly compilation, I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.

Thanks for your interest in this project. If you have questions or comments, please let me know, either here on the blog – there’s a page for Questions– or contact me by email at rigibson at earthlink.net. I’ll try to respond. You can of course also leave a review on iTunes. I really do appreciate your feedback.

For 2016, I’m going to TRY to have more frequent new programs than I did in 2015. Some upcoming topics, many suggested by you listeners, include fluorescence in minerals, questions about the oxygen crisis back in the Precambrian, the Tepuis in South America, and more. Thank you!

—Richard I. Gibson