About the blog: What Things Are Made Of

AMERICA'S GLOBAL DEPENDENCY FOR NEARLY EVERYTHING


The United States relies on imports for dozens of commodities in everyday use. Often enough, that reliance is 100%. In this book I aim to provide awareness of the hidden geology and mineralogy behind common things, and to develop an appreciation for the global resource distribution that underpins our society. While concerns about oil import reliance are in the news every day, our needs for other minerals are comparable and are typically unknown even to technologically aware Americans.





Wednesday, January 12, 2011

Arsenic

Orpiment (arsenic sulfide)
Arsenic is Bad Stuff. It may have contributed to Napoleon’s death (accidentally or otherwise) and its presence in water supplies is an ongoing concern. For many years the wood treatment industry in the US consumed most of the arsenic used here, because it is an excellent preservative and insecticide. But toxicity issues led the industry to voluntarily cease using chromated copper arsenate for human-contact lumber like decks and picnic tables in 2003. Total US arsenic consumption has fallen from more than 30,000 metric tons in 1998 to 3,600 tons in 2009.

But arsenic finds its way into a lot of other critical but low-volume uses. It strengthens grids in lead-acid batteries, combines with other metals in some ammunition, and is a vital component of semiconductors in solar cells, circuit boards, and telecommunication electronics. Light-emitting diodes (LEDs) in computers, CD players, and numerous other household electronic devices contain gallium arsenide phosphide in tiny amounts. Two pounds of gallium arsenide can make 500,000 LEDs.

There are some arsenic ore minerals, mostly arsenic sulfides like lemon-yellow orpiment and red-orange realgar, but the primary ore is arsenopyrite, iron arsenic sulfide. It is also common in other minerals mined for elements like copper, and arsenic contributes significantly to environmental problems in copper-mining regions.

All US arsenic is imported. 86% of arsenic metal comes to the United States from China, which produces about half the world’s arsenic.

Orpiment photo from USGS via Wikipedia (public domain).

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