Antimony: A Critical Mineral




Look how careful these scientists are with that material!

And yet people in the past used it all the time:

  • Ancient Egyptians might have considered antimony strategically important, just as the US does today, but for different reasons. Instead of using it for batteries, flame retardants, synthetic materials, and military purposes, they made eyeliner with it.

    Screenshot_2018-06-10-15-24-50

    Nefertiti. (Arkadiy Etumyan, CC BY-SA 3.0)


  • The Arab word that Europeans first translated as “kohl” is al-kuhul, derived from kahala–to stain or paint. Medieval alchemists turned this into the Latin alcoholpowdered ore of antimony! They thought it would lead them first to something called philosophical mercury and then to the Philosopher’s Stone. “Alcohol” later came to mean any powder or liquid that remained after vaporization; the word didn’t acquire its boozy connotations until the 18th century, around the time that antimony was in use as a pigment again.

    Screenshot_2018-06-10-15-27-56

    Matthias Stom used antimony-based Naples Yellow in “The Arrest of Christ.” (Source)


It’s unclear if antimony harmed anyone back then, but it could have. While antimony’s effects on human health vary, it can cause liver, skin, respiratory, and/or cardiovascular problems.

Also, in some formulations antimony will burn (a feature that chemical experts have harnessed to provide us with green and white fireworks, as well as “glitter” effects).

Antimony is obviously a multipurpose (and sometimes sparkly) element. But why did the US government list it as a critical mineral in 2018?

Introducing antimony (Sb)

Elemental antimony looks like a metal (and has been mistaken at times for both silver and lead).


stibnite

Fabulous! (James St. John, CC BY 2.0)


It also sometimes acts like a metal, but antimony is too brittle to use on its own. That’s why there are so many antimony alloys, including the plates and terminals of lead acid batteries, one of this mineral’s major commercial uses.

All of antimony’s other properties are similar to nonmetals. The way it react with halogens, for example, makes antimony an excellent flame retardant. It also serves as a catalyst for producing everything from Dacron to plastic bottles.

Chemists call such metal/nonmetal elements “metalloids.” The technical definition of this term is blurry, but four of the six most widely accepted metalloids (green ones in the table below)–antimony, arsenic, germanium, and tellurium–are on the US critical mineral list.


Metalloid table image

Links only work at the image source


So let’s get down to the major question here.

Why is antimony a critical mineral to the US?

As we saw with aluminum, the most important minerals from a strategic standpoint are those that are used in small amounts for specialized purposes, can only be produced as byproducts, and have no effective substitutes.

Antimony certainly meets the first two criteria.

  1. Relatively small amounts of it are needed for alloys and in chemicals, and some antimony applications (like thermal imaging, fining microbubbles out of glass, and as diodes in microelectronics) are highly specialized.
  2. While there is still a little pure antimony ore around, most of it is a byproduct of mining and refining stibnite and other ores. This process is complex and it’s also rough on the environment.

Now we’re going to journey back in time to Stibnite, Idaho. It produced 98% of the antimony the United States needed to fight World War II, as well as much of its tungsten.

After the war, better deposits were found elsewhere, and the place shut down. Today, the open pit mine shown at around 3:40 is a lake.

By the way, not Indiana Jones.



This look at an old-timey operation that helped us fight WWII brings us to why antimony is critical to the country’s economic and national security in the 21st century:

In an analysis of strategic mineral supplies prepared prior to World War II, Roush . . . stated that “Antimony has more uses of a direct military character than other members of the strategic [mineral] group and probably more important uses than any of the others except mercury.” In addition to serving as a combustion-supporting ingredient, antimony has important additional uses for the military, some of which were first exploited in the Russo-Japanese War of 1905 and, later, by the United States during World War I . . . Antimony is a hardening agent in metals used in ball bearings, bullets capable of penetrating armor plate, and lead shot. It helps to strengthen cable sheaths, chemical pumps, foils, plumbing fixtures and pipes, roofing sheets, and tank linings. During World War II, the fireproofing compound antimony trichloride (SbCl3) saved the lives of many American troops when it was applied to tents and vehicle covers. In a fire, antimony and chlorine recombine to form unstable compounds that remove oxygen from the air, smothering the flames . . .

— Seal, II, and others (see source list)

Those combustible forms of antimony, besides their use in fireworks, are key ingredients in ammunition primers, detonators, smoke-screen generators, visual range-finding shells, and tracer rounds.

Antimony also increases heat tolerance in graphite bearings and is an excellent alloy for frictionless ball bearings. It is part of rubber vulcanization and even serves, along with beryllium, as a start-up neutron source in nuclear reactors.

Overall, this mineral’s strategic value is so important, and there is so little of it in North America, that people are thinking seriously of reopening parts of that Idaho district–now a national forest–to mining.

They’re even doing some mineral prospecting.



Yes, that’s controversial, but it’s important to realize that this isn’t a zero-sum situation. We need to find some middle ground between the extremes of exploitation and national/environmental protection that the widest number of individual interests can accept.

No, I don’t have an answer.

Green and white fireworks we could probably live without, if we had to; plastic bottles are recyclable, as are lead acid batteries; but what about the flame-proofing in my mattress, clothes, paint, paper, fiberglass, and other materials?

And, while everybody wants peace all of the time, the variety of antimony-based military tools that the US, like all modern countries, has in its arsenal need to be there, if only to ensure that something like the world events of the late 1930s and early 1940s never reoccur.

Fortunately, there is no shortage of antimony, just an imbalance in the world’s supplies, thanks to geology. Most of the world’s antimony comes from stibnite ore, and the major reserves are in China, which produced almost 80% of the world’s antimony metal and oxides in 2015.

Actually that was big decrease in production (2011 was the peak year for Chinese antimony production). The government there is cutting back on antimony mining, partly because of low prices, but mainly because of environmental concerns. Stibnite has a lot of sulfur in it, as well as arsenic and mercury in some ores. And then there is the coal needed to run the smelters.

Hunan Province, where most of the antimony is mined, is three provinces due south of Shanxi Province, where the following video was filmed, but as they say, the air is bad all over the country. Antimony mining and smelting just make it worse.



And here we are, at the thorniest issue, and therefore, the place where a middle ground is especially needed today.

Experts (Seal, II, and others) think that the present rate of mining and smelter production, as well as battery recycling, will meet global antimony demand for the foreseeable future, barring market manipulation.

But we don’t really want to maintain the status quo, do we?

Of course, no one wants a return to those devastated Idaho mountain forests and hills shown in that 1950s-era Stibnite, Idaho, video. Nor is it right that mountain peaks are now being disassembled in our search for this critical mineral.

But who wants a world where some people must live with filthy water, poisonous streets, and a dim Sun so that the rest of us can enjoy scenic vistas and a much cleaner environment?

We really need to find some middle ground here. And again, no, I don’t know what it is. But now you’re thinking about it, aren’t you.

That’s a start.

Whatever the solution to this imbalance of pollution may be, while searching for it we will also discover better ways to balance the global supply of this modern critical mineral, antimony.


5052124921_d11d92ca4b_z

Fabulous.



Featured image: Stibnite, by James St. John, CC BY 2.0.



Sources:

Agency for Toxic Substances and Disease Registry. n. d. Summary chapter: Toxicological Profile for antimony, CAS #7440-36-0. Centers for Disease Control. https://www.atsdr.cdc.gov/phs/phs.asp?id=330&tid=58 Last accessed June 9, 2018.

Graedel, T. E.; Harper, E. M.; Nassar, N. T.; Nuss, P.; and Reck, B. K. 2015. Criticality of metals and metalloids. Proceedings of the National Academy of Sciences, 112(14): 4257-4262.

Harper, Douglas. n.d. Etymology Online. Last accessed June 9, 2018.

Klochko, K. 2018. Mineral commodity summary: Antimony. USGS. PDF

—. 2017. Antimony (advance release). USGS 2015 Minerals Yearbook. PDF.

Seal II, R. R.; Schulz, K. J.; and DeYoung, Jr., J. H., with other contributors. 2017. Chapter C: Antimony, in Critical mineral resources of the United States—Economic and environmental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, Schulz, K. J.; DeYoung, Jr., J. H.; Seal, II, R. R.; and Bradley, D. C., eds. https://pubs.er.usgs.gov/publication/pp1802

Thomas Jefferson National Accelerator Facility – Office of Science Education. n.d. It’s Elemental – The Element Antimony. https://education.jlab.org/itselemental/ele051.html Last accessed June 9, 2018.

Welle, F., and Franz, R. 2011. Migration of antimony from PET bottles into beverages: determination of the activation energy of diffusion and migration modelling compared with literature data. Food Additives and Contaminants, 28(1): 115-126.

Wikipedia. 2018. Last accessed June 9, 2018.


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