View single post by Keith Pashina
 Posted: Wed Mar 15th, 2017 04:02 am
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Keith Pashina

 

Joined: Sun Nov 4th, 2012
Location: Minneapolis, Minnesota USA
Posts: 566
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Thanks everyone for the nice comments on this discussion. It's been a while since I posted, so here we go again...


A SUMMARY OF MILLING PRACTICES USED IN BLACK HAWK
 Example of the stamp heads with the front screen in the mortar box removed. This stamp mill display is actually in Leadville but the Gilpin County mills were similar


In the previous posts, we looked at the most visible and well known processes in a stamp mill:
 
·       Initial crushing and ore handling
·       Stamp mill crushing and amalgamation
·       Amalgamation tables and blankets
·       Mechanical ore concentrators – Gilpin County bumping tables and others
·       Secondary mechanical ore concentrators – Frue vanners
·       Mercury retorts for initial amalgam processing
 


But, there is a lot more to ore processing, we’ll look closer at some equipment. Remember, our goal here is to learn enough to understand the basic processes and build plausible models. There are an awful lot of technical issues that were considered by the mill operators that we can skim over – partly because it doesn’t matter in the models and partly because I, a non-mining engineer, wouldn't understand anyway!
 


Most of the gold ore flowed through the mill in linear process: crush, amalgamate, concentrate, and process concentrates. But, there are always exceptions, and Black Hawk mills were all similar, yet no two were fully alike.
 


Cross-section of a common stamp mill in the western United States - but, as will continue to see, mills configured like this one were the exception, rather than the rule, in Gilpin County




From the 1917 Economic Geology report on Gilpin County, a comparison of Black Hawk mills then operating shows nine of the fifteen then-operating miils used a combination of stamps, amalgamation plates and tables, and either Gilpin County Bumping Tables or Wilfiey tables:
 
·       Brooklyn Mill (used jigs, too)
·       Buell Mill (in Mountain City)
·       Eagle Mill
·       Fifty Gold Mines Mill
·       Hidden Treasure Mill
·       Polar Star Mill
·       New York Mill
·       Randolph Mill
·       Wheeler Mill
 


There were four other mills that operated in the 1800s and earlier in the century, but were not in operation at the time of the 1917 report. I don’t know for certain what all the equipment used, but the Sandborn Fire Insurance maps seem to suggest these used stamps + amalgamation + bumping tables or similar equipment:
 
·       Kimber & Fullerton Upper Mill
·       Meade Mill
·       Golden Gilpin Mill
·       Rocky Mountain Concentrator
 


There two other mills that used this equipment in 1917:
 
·       Frontenac (Iron City) Mill (Stamps, Amalgamation, Callow cone thickeners, trommels, jigs, Flood classifiers and Card & Deister tables)
·       Clear Creek Mining & Milling Co. Mill (Wilfley tables, Frue vanners, bumping tables, and canvas tables)
 


So, we’ll next look at what happened in the mills to further concentrate the ores after they passed through the stamps, crossed the amalgamation tables, and ran through the bumping tables and Wilfley tables.


Keith

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