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Bauxite is an mineral of Aluminum. Despite a general mineral wealth, the USA does not have any major Bauxite deposits, except for one in Arkansas. The mining town was named Bauxite, Arkansas.

The mine operated from 1895 to 1981. It produced about 80 million metric tons of bauxite ore over its lifetime (just guestimating from this pdf, page 6).

So what is the origin of this deposit? It seems strange to me, not being near any mountains. How did the minerals form? And why aren't there any others despite very similar terrain all over Arkansas and other states?

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  • $\begingroup$ Are you asking about how bauxite is formed in general? Or are you presupposing people know that, and are just asking about Arkansas? $\endgroup$ – Spencer Feb 17 '17 at 3:03
  • $\begingroup$ @Spencer How it's formed in general and what prevented more Bauxite from developing in the similar surrounding area of Arkansas. $\endgroup$ – DrZ214 Feb 17 '17 at 4:21
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    $\begingroup$ "80 metric tons" is a minuscule amount of material to mine, particularly over an 86 year period, from 1895 to 1981. I would have expected something closer to 80 Mt (80 million tonnes, or for the non metric parts of the world 80 million metric tons) over that time period. $\endgroup$ – Fred Feb 17 '17 at 7:18
  • $\begingroup$ @Fred yes it's 80 million metric tons, typo or mentalo confusing metric/M. Edited. $\endgroup$ – DrZ214 Feb 17 '17 at 9:37
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The short answer is, bauxite requires a particular alumina-rich source rock and a specific set of conditions and processes to concentrate the aluminum in a specific order.

From the Encyclopedia of Arkansas:

The Arkansas bauxite region covers about 275 square miles in the northern part of the West Gulf Coastal Plain and is divided into two mining districts. One area is in Pulaski County, south and east of Little Rock, and the other is in nearby Saline County, northeast and east of Benton.

Generalizrd geographic map of Arkansas

(Source, Arkansas Geological Survey; a very detailed map can be downloaded here)

The source rock (nepheline syenite) for the bauxite appears as two isolated blue spots in the middle of the map above, surrounded by (orange) Tertiary sedimentary deposits. The town of Bauxite is just to the northwest of the southern spot.

Rather than cut and paste EOA's description of the process, I decided on the following summary:

  • Magma was intruded during a Cretaceous volcanic event as the Mississipi Rift opened, and this formed nepheline syenite, which has aluminum-rich nepheline where granite would have quartz.

  • The syenite decomposed, eroded, and was deposited as a soil on the edge of a shallow sea that filled the rift.

  • In the Paleocene, tropical conditions caused the aluminum minerals toleach down into the soil, becoming concentrated into a hard layer called a laterite

  • In the Eocene, some of the laterite was eroded and deposited as alluvial bauxite ore as the sea slowly filled in.

Both the original laterite and the alluvial deposits have been mined for aluminum.

Your assertion that there are no other bauxite deposits in the US is not true; other deposits formed in similar conditions in the southeastern US, and there is also bauxite in Montana.

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  • $\begingroup$ I never asserted that there were no other bauxite deposits in the US, only that there were no other major ones. Given that the others in that list make up 10% combined of Bauxite Arkansas, I'd say it is still true. $\endgroup$ – DrZ214 Feb 17 '17 at 22:47

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