National Mining Hall of Fame and Museum - Leadville, Colorado, minerals, gems, history

     John Van Nostrand Dorr invented many devices that greatly increased the efficiency of the cyanide method of gold extraction and were later applied to other industries.

     Dorr began his career in the laboratories of Thomas Edison.  Later, while working as an assayer and metallurgist in the gold mills of South Dakota and Colorado he invented the Dorr Classifier.  Although the Classifier was initially used for the continuous extraction of gold by the cyanide process, its use rapidly spread to many industries.  Of the more than 20 patents awarded him, the most important include:  the Dorr Thickener: for the continuous thickening of ore slurry, and the Dorr Air-Lift Agitator; for the continuous mixing of liquids.  These 3 inventions had a huge impact on the processing of mining materials by hastening the transition from intermittent to continuous processing.  Later the Dorr Thickener became a basic tool used in water and sewage treatment plants and the sedimentation processes he invented rendered economically feasible the desilting of water from the Colorado River for use in irrigating California's rich Imperial Valley.  Many of his inventions form the basis for the modern sugar industry.

     Few men have had such an enormous impact, not only on the mining industry, but on many industries around the world with his invaluable inventions and technological processes.