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Modeling the Gilpin Tram Part I
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 Posted: Sun Nov 18th, 2012 11:39 am
   
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elminero67
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The stamp mill model is a beauty, really captures the feel of the prototype.

Great to see that people in Colorado have embraced (to a degree)the mining culture and preserved some of the mines and mills rather than bulldoze them in order to make way for more McMansions.



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 Posted: Sun Nov 18th, 2012 12:51 pm
   
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W C Greene
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Amen, brother! I have looked at Keith's modeling for years now and I have come to the belief that besides being a fine historian, he is a master modeler. Wow, we have two such fellows(Keith & Duane) right here on Freerails, artists and writers, who have inspired me greatly. Thanks guys.

Woodie



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 Posted: Sun Nov 18th, 2012 03:57 pm
   
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Keith Pashina
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Woodie, Herb, Duane, and Bernd - thanks for the nice comments.  It's fun sharing and discussing this stuff with all of you.

 

Bernd - you asked about the Polar Star Mill, and noted it doesn't look like most stamp mills we are all familiar with.  The mines around Central City- Black Hawk were first developed early on - this was the general area of the "Pikes Peak or Bust" gold rush in the mid-1850s.  There were three or more waves of development in the industry, and many of the mills, such as the Polar Star, were built maybe a decade or more before the Gilpin Tram was built. 


These mills still used stamps to crush the ore, amalgamating tables, and other equipment we have used elsewhere.  The Gilpin County stamps were referred to as "slow drop" stamps, running with heavier heads, but a lower rate to crush the ore.  One of the pieces of equipment used was the "Gilpin County Bumping Table", which was bumped back and forth to separate the metal from the waste.  We modelers are more familiar with the Wilfley table, which was developed at a later date, but has been made as kits in several scales.

 

So, Bernd, that's a long-winded answer to say these are still stamp mills, just a little different.


This is a photo of typical stamp, displayed at the Central City historical society museum.  The  image below shows a Gilpin County Bumping table - kind of a cruder version of the Wilfley table.


So, several mills were built on the low, barn-like appearance such as the Polar Star Mill.  Several other mills looked like the more typical stamp mill construction we are used to seeing.  Besides the Iron City Mill, there were several others.


The Avon Mill was served by the Gilpin Tram - that's the mainline to Quartz Hill in the foreground.


The Oliver Mill was located in Chase Gulch, about 1/2 mile above Black Hawk.  The Gilpin Tram ran on the hillside above the mill, but it may have had a spur serving it at one time.


This small mill still stands, and can be seen next to the highway between Central City and Black Hawk.  This was never served by railroad, but is very modelable size.  This structure was brought as a kit by Wild West Scale Model Builders in multiple scales (sorry Wooide, not in 1:35).

 

Keith

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 Posted: Sun Nov 18th, 2012 04:41 pm
   
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Herb Kephart
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Keith, do any of the mills still standing have any processing machinery in them?

Herb 



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 Posted: Sun Nov 18th, 2012 08:49 pm
   
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elminero67
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Keith hit the nail on the head-many of the mills in Blackhawk were built before the stamp mill evolved into the form we come to recognize as a "stamp mill"

Dont want to highjack Keith's thread and go on one of my infamous, verbose,nefarious, agregious and outragious rants on the misconception of what a stamp mill should look like and how it is modelled...Got me speakin' like Al Sharpton...



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 Posted: Mon Nov 19th, 2012 10:34 am
   
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Keith Pashina
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Al, er, I mean Duane: please give us your thoughts on stamp mills! As far as I am concerned, the more, the better!

Herb, you asked if any of the mills have machinery in them? By my count, there are 5 mill structures still standing in the area: Polar Star and the Golden Gilpin Mill in Black Hawk, the Little Red Mill in Mountain City, an unnamed mill remnant in Illinois Gulch, and the more recent Chain-O-Mines building in Russell Gulch.

I think only the Golden Gilpin Mill and Chain-O-Mines mill have machinery in them, and these are more recent mill buildings - 1950s is my guess. Neither were served by the Gilpin Tram.

I was given a tour by the Polar Star Mill's owner, and none of the original machinery remains.

There were a few more pieces and remnants of mills that are around, or disappeared in the last 20 years - I'll post more on those if there is interest in that topic.

Keith

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 Posted: Mon Nov 19th, 2012 12:11 pm
   
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Bernd
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Keith,

Thanks for that explanation. I'm finding this very fascinating. When I first read about a "ten stamp" mill I wondered what the heck is that. The I finally found the answer. I believe the Gazette had some article a while back about these mills.

Another thing, didn't they use mercury to separate the gold by, for lack of a better word, foaming it to separate the gold form the overburden?

Bernd



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 Posted: Mon Nov 19th, 2012 12:30 pm
   
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W C Greene
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Funny that you should mention mercury in gold/silver smelting. Here is a photo of a little mercury still I built from the idea of Verne Niner's. If you search for mercury still here, you will find info about these things. They were built a ways from the smelter (even the toxic smoke couldn't compete with mercury distilling).




The mercury was distilled from the ore and it dripped (I suppose) from the pipe on the left side. It filled bottles which were then taken into the smelter. The info and history of these things are in Verne's thread so I won't cover it here. You might note that the usual sparse vegetation is REALLY sparse here since the mercury killed off anything close by! This little still is about 8 by 8 feet and about 8 or 9 feet tall.

Woodie
http://www.freerails.com/view_topic.php?id=1964&forum_id=4&highlight=mercury+still

That's the link for the thread...



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 Posted: Mon Nov 19th, 2012 12:34 pm
   
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Sullivan
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Mercury distilling also killed off the workers. It was the original Zombie maker of the smelting industry. After years of being subjected to the toxic vapors they would begin drooling and become palsied.

And, yes, you're correct that the vapor accumulated in the top of the boiler and there was usually some kind of pan or pipe that would collect it as it cooled and allow it to drain into the transfer bottles or flasks (made of iron).

Last edited on Mon Nov 19th, 2012 12:40 pm by Sullivan



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 Posted: Mon Nov 19th, 2012 03:04 pm
   
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Keith Pashina
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Bernd:

My understanding of the process is (spoken as a Civil Engineer, not a mining engineer, and not even living in Colorado) was mercury was spread over copper plates, call amalgamating pans, which were sloped sheets directly in front of the stamp mill. As the slurry ran across the amalgamating pan, free gold would stick to the mercury. The rest of the slurry, still containing some gold, would be concentrated further by other processes.

Periodically, the stamp mill would be shut down (a very interesting process in itself), and workers would use wood paddles to scrape off the amalgam - mercury, gold, and other metals, for separation in the mercury still.

A Gazette article by Hitzman about 1987 had very good article on this. I think the mercury still, as shown in Woodie's photo, basically heated a sealed metal pot with a tube coming out the top. As the vessel heated, the gold melted, and the mercury boiled off. The tube coming out of the vessel was submerged in water, and the mercury gas condensed into a separate vessel. The tube coming out the side of the still theoretically had only water vapor in it, but some residual mercury was lost, too.

It must have been a smelly, hazardous mess in some of those ore processing towns.

Keith

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