Arsenic: A Critical Mineral

This element is colorless, tasteless, inexpensive, and deadly–oh, and as a compound it can turn electricity into light (as in LEDs, fiber optics, telecommunication, and laser scanners).

That last “Star Trek”-style application is just one of the reasons why this “Murder She Wrote” element is on the 2018 US critical minerals list.

What is arsenic?

You might be thinking, wait, arsenic is a mineral? It’s not a nefarious white powder?

That powder exists, but it’s artificial. Arsenic itself is a metal–one of the weird ones that have a few nonmetal properties. As the chemical element As, it belongs in the same group of metalloids as antimony (Sb), another critical mineral.

Metalloid table image

The metalloids are green. Reading vertically, from top to bottom, arsenic is in group “15”–the nitrogen group–on the periodic table of elements. This matters for arsenic’s use as a semiconductor in electronics and telecommunications. (Links are live at image source.)

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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.


    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.


    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?
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Aluminum: A Critical Mineral

Most residents of the United States think of foil, beverage cans, and recycling when we hear the word “aluminum” (or “aluminium”); then lots of other things come to mind, including vehicles, aircraft, and various items in our homes and offices.

Aluminum is even more widespread than we realize. As a metal, it’s also used in construction and for electrical power systems, including wires and cables. Many machines are made of aluminum, too.

As alumina–powdery aluminum oxide–it’s present in industrial refractories and many chemicals down to and including the main ingredients in styptic pencils and antiperspirants (alum–a naturally occuring aluminum salt–has been used as an astringent for centuries).

Aluminum is obviously common and inexpensive, so why is it on the US government’s 2018 “endangered minerals” list?

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Guest Video: Critical/Strategic Minerals

An update on this February 2018 post is needed because the US Department of the Interior recently issued its final list of critical minerals (see end of post).

Gold, silver, and gems aren’t the only treasures out there. The materials that make our modern life possible aren’t always pretty, but they are very important. The rare ones, like the platinum group elements, are also expensive.

Recently, the US government put together a list of the minerals that it considers to be most important to the security and economic welfare of the country. While insiders recognize a difference between “critical” and “strategic,” in practice the two are pretty much the same minerals.

This list has a link for each of the 35 minerals, showing how they are used and lots of other information.

In addition, here is a webinar on critical minerals from 2016.

Update: On May 18, 2018, Interior issued its final list, which is the same as the proposed list:

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