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Hall of Fame - John Van Nostrand Dorr: 1872-1962; Dr. James Douglas: 1837-1918.

HALL OF FAME (The National Mining Hall of Fame & Museum is located in Leadville, Colo.).


John Van Nostrand Dorr, a major contributor and pioneer in the history of precious-metal milling technology, developed several inventions that greatly increased the efficiency of the cyanide method of gold extraction.

Dorr began his career in the laboratories of Thomas Alva Edison at the age of 16. After graduating from Rutgers University, he worked as an assayer, chemist, and metallurgist in the gold mills of South Dakota's Black Hills and in Colorado.

In 1913, Dorr undertook the operation of a small mill in South Dakota for the extraction of gold by the cyanide process. The ore was treated with a cyanide solution and the dissolved metal was later precipitated from the solution, fused, and cast into ingots. There, Dorr invented the Dorr classifier, an apparatus for separating fine and coarse material in an ore slurry on a continuous basis, rather than through the standard, single-batch processing technique.

Although the Dorr classifier was initially used for continuous extraction of gold by the cyanide process, its application also permitted the profitable recovery of silver and other materials from sources previously considered worthless. Its use spread to similar processing operations in many different industries. At approximately the same time, he invented two other devices, both for ore processing, which were successfully applied to other industries. These were the Dorr thickener, for the continuous settling and thickening of ore slurry, and the Dorr air-lift agitator for the continuous mixing of liquids or the extraction of solubles from finely divided solids by means of an air lift. These three inventions had a huge impact on mining and beyond by hastening the transition from intermittent to continuous processing, thus allowing mass production in many different industries. The terms classifier and thickener, first used by Dorr to describe his inventions, rapidly became part of standard engineering vocabulary.

Among the more than 20 U.S. patents awarded Dorr, the most important include, the Dorr classifier, the Dorr thickener, a tray thickener, a thickener-hydrometer, and the renowned Dorr agitator. The Dorr thickener and Dorr clarifier became the basic tools used in water and sewage treatment plants. The sedimentation processes developed by Dorr made the desilting of water from the Colorado River economically feasible. Such water is used for irrigating California's rich Imperial Valley.

Few men have had such an enormous impact, not only on the mining industry, but also on many different industries around the world, as did John Van Nostrand Dorr with his priceless inventions and technological processes.

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Title Annotation:National Mining Hall of Fame & Museum
Publication:E&MJ - Engineering & Mining Journal
Date:Sep 1, 1989
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