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Modeling the Gilpin Tram Part II
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 Posted: Sun Feb 19th, 2017 08:55 pm
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oztrainz
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Thanks Keith for the detail on ore processing at Blackhawk. 


It is interesting that Blackhawk developed differently than the most of the other "Colorado" mining areas and that the mill layout and equipment was significantly different. 


Your explanation of how some of this stuff works is some of the best I've seen (and I've read a few of the older ore processing books that I've picked up at old book marts or online). You have probably got enough stuff on both of your Gilpin threads here for a history Doctorate. 
Well done and please keep the updates coming, 



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 Posted: Wed Mar 15th, 2017 04:02 am
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Keith Pashina
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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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 Posted: Fri Mar 17th, 2017 03:29 am
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Chriss H
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I can't imagine just how loud it would be inside a stamping mill (especially one with 70+ stamps running), not to mention outside in a house next door! All the equipment looks very loud, even the wiffley tables.



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 Posted: Sun Mar 19th, 2017 10:59 pm
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Chriss H
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I'm pretty sure this PDF has not been mentioned by Keith or any other poster in the first Gilpin Tram thread #1. It is an interesting, but dry document, on The Gilpin Tunnel Corridor from 2009, put out by the County of Gilpin, CO to study feasibility of historical properties. Lots of photos of some of the older still standing homes and buildings along the Gilpin Railroad area.
http://www.co.gilpin.co.us/Auxiliary%20Advisory%20Boards/Historical%20Society/Gilpin%20Tunnel%20Rail%20Corridor_Final%20Report_SWCA.pdf
I tried to attach it but it's size is just a tad too big at 5.7MB.



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 Posted: Mon Mar 20th, 2017 02:31 am
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Keith Pashina
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Chriss,

Thank you for posting that link to the northern Gilpin County historic document. It seems to be a private consulting firm's report on a survey on potential historic properties along the former Denver & Salt Lake Railroad, where it traversed northern Gilpin County. Lots of detail there on several very interesting structures.

Also, the noise in a mill must have been terrific. There are accounts of the constant rumbling in the background that residents heard - it became a part of the normal background noise, and would wake people up if the mills stopped. I saw a demonstration of a 5-stamp stamp battery at the Western Museum of Mining (near Colorado Springs). That single stamp battery was very loud!

Keith

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 Posted: Mon Mar 20th, 2017 02:45 am
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Keith Pashina
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The inside of the Iron City (Frontenac Mill), showing Deister tables - a piece of equipment similar to, but differing from the more-commonly used Gilpin County bumping tables and Wilfley tables


More Ore Concentrating Equipment


Now, we’ll take a short 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. To make some generalizations, ore concentrates were handled by a variety of secondary concentrating processes, and the equipment used would make some very interesting models.
 
In my previous post on March 14, 2017, I listed the mills operating in 1917 – most used a simple combination of stamps, amalgamation plates and tables, and either Gilpin County Bumping Tables or Wilfiey tables, Only two mills at that time did anything different. However, the 1917 report is merely a “snapshot in time.”  Many of the mills evolved in their processing over time – we have already seen that in the Hidden Treasure Mill. This seemed to happen in many of the other mills also. So, when modeling an ore mill, I will need to select a particular year if I really want to be that accurate.
 
When the ores were crushed, there was a fine line between crushing the ore not enough or too much. If not crushed enough, the particles were too large to adhere to the mercury on amalagamation plates or separate easily on bumping tables. If the ore was crushed too fine, the slimes (fine particles suspended in water), would pass over the amalgamation equipment and bumping tables. It was inevitable that some particles would be very fine, and this one reason why secondary concentrating processes were also used at many mills.

The secondary concentrating equipment generally seemed to include three types of machinery:
 
1.     Concentrating tables or jigs
2.     Gravity separation in tanks or buddles
3.     Additional grinding equipment to rework the ores




The Card concentrating table for slimes - used in the Iron City/Frontenac Mill and others
More on Concentrating Tables 
To further concentrate the finely crushed ore particles, there were many different options available. Sometimes, a second group of Gilpin County bumping tables would be used. Wilfley tables were sometimes used, as well as Frue vanneers, Card tables, and Deister tables. All of these tables operated in a similar fashion – a bed with small ridges was bumped, shaken, or vibrated when the ore slurry passed over it. Often, the speed, ridge size, slope, etc. were customized for a certain size ore particle and specific sources of ores. This doesn’t really matter to me much – I care more about what the machinery looked like and its general location within the mill.
 
To me, all of these equipment looks similar, varying in size and general layout of operating drive wheels, gears, and movement arms. WIlfley tables are the only concentrating equipment I have seen offered as kits in my scale, HO, but I think they have been offered in O and maybe S, too.
 
I probably need to create a master for Gilpin County bumping tables, and either cast a few in resin, or print in 3D.


The Deister table was another type of concentrator used in some Black Hawk mills. This company is still in business manufacturing equipment for the mining industry




Example of a jig - this type may or may not have been used in Gilpin County mills. This type had a metal ore working box
Jigs

I haven’t mentioned the other concentrating equipment group yet – jigs. These machines took the ore slurry, and agitated it in water with added chemicals. The chemicals were oils or oil-like compounds, and the agitation produced an oily froth to which gold particles adhered. The froth was skimmed from the top by the jig to collect the gold. Think of a washing machine type apparatus and you have the general idea.

What is interesting from a modeling point of view is that the jigs look like large square tubs with wheels and gearing on top. I have never seen these offered in kit form, but these would be relatively easy to model. Again, probably a candidate to cast in resin or print in 3D.
 


Another type of jig - this type has a lower wooden box. From remnants of jigs I have seen in Gilpin County, I think this type was more commonly used than the metal box type shown in the preceding photo. This wooden box type could be scratch built with some effort - I don't know how common the elaborate cast iron bracing shown was - the examples I have seen, although more modern, were much simpler
The next group of concentrator equipment were those that used gravity to separate out the heavier gold and other metals from the lighter crushed minerals. This will be my next post.


Keith

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 Posted: Mon Mar 20th, 2017 03:00 am
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Keith Pashina
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Nope, I lied!

After I typed the last post, I realized I had forgotten to show any contemporary photos of jigs. 



This schematic is from the 1907 Colorado Iron Works Catalog, and shows the general arrangement of how a wooden box jig was laid out - this one would have been belt driven from a central steam or electric engine

These mostly intact jigs are on display next to the Couer D'Alene Mine, a restored historic display in Central City

Joe Crea and I were exploring the Pittsburg Mine and Mill (just south of Central City), and at the bottom of the ravine are some jigs. This particular one is badly decayed, but it shows that most of the jig was of wood construction, with some fairly basic metal parts - making jigs relatively easy to model

This is the inside of a jig box at the Pittsburg Mine and Mill. The metal drive mechanism and agitating equipment have been removed. In a model, you don't need to model what's going on inside the jig, since it would be filled with slurry anyway
Keith

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 Posted: Mon Mar 20th, 2017 03:22 pm
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Chriss H
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Really good stuff Keith!
..
I'm waiting for the HO scale models from http://www.westernscalemodels.com to begin selling all those neat detail parts of a stamp mill, they've had the O scale parts done for awhile now. The detail bits they have look great. They should really jazz up my models!

With your information it will help greatly in recreating a believable mill interior.



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 Posted: Sat Apr 1st, 2017 05:10 pm
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Keith Pashina
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Now, we'll conclude the overview of Black Hawk milling machinery, with a look at some more of the secondary concentration and cleanup equipment.
Concentrating tables and jigs were looked at in my previous posts. So, to better capture the slimes, the too-finely crushed ore particles, other processes included gravity separation in tanks or buddles, and the use of additional grinding equipment to rework the ores.
 




BUDDLES
 
Buddles were commonly used in the Black Hawk mills, at least in the early years. Buddles were of two types – stationary and revolving. The stationary types basically ran the slime or slurry down a small trough, to the top of a cone-shaped table. The cone evenly distributed the slurry out into a shallow square or circular box (both were used). Some buddles were small, perhaps 8’ x 8’, but could get larger – some districts used buddles up to 16’ diameter, but I don’t know if this was used in Gilpin County. Gravity separated out the heavier metal particles from the lighter sand-like materials – the lighter sands spread out near the perimeter, and the heavier particles near the center. Once the shallow box was filled, the valuable concentrate was hand-shoveled out, and then the sands shoveled out and disposed of. Very labor intensive, but also very simple, too.  This equipment hasn’t been offered as kits, but it wouldn’t be that hard to scratchbuild, either.
 


Slime tables differed from buddies - the separated sands and concentrating were washed off, whereas a buddle collected the material inside the box or tank. Every so often, the flow was stopped, and the waste and concentrates hand-shoveled out




The above view shows a Callow cone inside the Frontenac/Black Hawk mill. A simple piece of equipment, easy to model. Also, note the electric motor and belt drive - this mill was a modern operation!


Remnants of a cone classifier by the Pittsburg Mill (about 1/2 mile south of Central City)
TROMMELS AND CONES
 
The next refinement was to mechanize the shallow conical table, so that it slowly spun clockwise while the slurry was run down over its center. By shallow, I mean the table sloped about 1½” per foot, and speeds were very slow, between 1 rotation per minute to 1 rotation per hour! Buddles would be a piece of equipment easy to model.
 
Other equipment used, particularly at the large Frontenanc/Iron City Mill, were cones and trommels.
 
Cones were similar to a funnel, and separated out heavier particles from lighter particles. Trommels were essentially a cylindrical rotating screen. This equipment would be interesting to model, although I have no idea how I would build a trammel in HO – trying to model realistic sized screen would be tough. I have seen no commercial models offered for this equipment.


Example of trammel

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 Posted: Sat Apr 1st, 2017 05:17 pm
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Keith Pashina
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Rod mills inside the Frontenac/Iron City Mill. Not available as a kit anywhere, but it wouldn't be hard to scratch build models off one




Another illustration of a rod mill
FINE CONCENTRATING/GRINDING
 
To also get the ores to a uniform size, and smaller than what stamp batteries and jaw crushers would provide, other crushing and grinding equipment was used – this was not all that common in the Gilpin Tram era, and seems to be a “modern” technology that came in in the 1900s. The large Iron City/Frontenac Mill did have this equipment, and maybe others did, too. Three types used were:
 
·       Ball mills
·       Rod mills
·       Chilean or Huntingdon Mills
 
Ball mills are a horizontal rotating metal cylinder, filled with large metal balls. As ore slurry is fed into one end, the gradual grinding action crushes the ore to a fine sand or powder like consistency.  Rod mills were also horizontal metal cylinders, but filled with metal rods, similarly crushing the ore.  The type of mill, speed of rotation, etc. were generally customized to the ores being processed at the time – there didn’t appear to be one universal standard.
 


A small ball mill, Russell gulch area


Once ore was concentrated further, where it went next for processing depended on the ore’s chemistry and mill practices. The concentrates might be run through more bumping, Wilfley, Card or other tables, or vanners, or jigs, or… From my limited reading, it seems sometimes one bumping or Wilfley table would be set up to process one very limited size of concentrate, and paired with that would be another one for the next smaller size, and so one. So, there could be multiple lines of concentrating tables lined up in a mill. Some photos seem to show two levels of tables, one row above the other, to do this.
 
But, not all ore went back onto tables, some of it, again depending on the mill and its practices, went onto final grinding and amalgamating.




A ball mill, this one with a conical shaped end

The inside of a partially dismantled rod mill - protective plates lining the metal barrel have been partially removed, and so have the steel rods that rolled around and crushed the ores

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