Thanks for all the quick replies guys! It's kept me busy over the last couple days.
Although one thing I can't seem to wrap my head around is how the gold bullion (or any ore for that matter) is shipped out from something like a early 20th century stamp mill, for instance. Is it just packed into burlap sacks at the bottom of the mill and loaded onto flatcars/boxcars via crews of teamsters, kept in an ore bin and dropped into hoppers on one of the lower levels, or would it just be smelted on-site into ingots and sent on it's way in inconspicuously marked crates with 'This is clearly not a box of priceless gold bars. Do not open.' stenciled smugly onto the side in paint?
In addition, is it worth considering the need to haul the stamp sand and tailings by rail to another location for disposal if the nearby geography was inadequate to provide an depressed area to fill in, or would it simply just be dumped off the side of the hill there anyway, and what sort of storage would the stamp mill need in order to load it into rail cars (I'm almost certain it's some kind of overhead bin or tipple) and would it be built into the mill building itself or exist as a free standing structure nearby (with the sand deposited via conveyor, I assume)? Same questions also with the lime, mercury, and cyanide components used in the washing process (though I'd venture to guess that those three may be a bit more sophisticated than a large wooden bin, given their potential volatility).
Hi,
I can offer a little help as I just finished Volume 2 of The RGS Story which covered Telluride and Pandora along with the surrounding mines and mills.
In the late 1800s, the mine complexes in the basins above Pandora varied depending upon their locations. Some of the first ones worked the exposed seams from the floor of the basins where there was enough room for a hammer mill. If there was a source of water available then the crushed rock would be washed and nuggets picked out by hand and bagged in burlap bags to be sent down the hill by wagon to Pandora. Here it would be loaded into boxcars and the car doors would be locked and a seal placed on the car doors by a mine worker. They were then taken to the smelter at Durango. This process left a good amount of gold, silver and other metals in the tailings by the mill but it wasn't consider cost effective to transport this lower grade ore to the smelter. Also mill workers were know to "pocket" a nugget when no one was looking.
Once these choice spots were claimed, other mines were left to work horizontal shafts into the walls of the basins to reach the seams. These mines didn't have room to build a mill so they used aerial tramways to send ore to the hammer mill at Pandora where it was processed and shipped as above.
Around the turn of the century, the milling process was improved with the introduction of the flotation mill. The hammer mill would crush the ore to a fine dust and that dust would be placed into large tanks were the metals would sink to the bottom while the light rock and sand would float on the froth generated by agitating the water with pressurized air. The froth and waste water would go to a settling pond. The hammer mill was later replaced by the ball mill where the ore would be placed in a large rotating drum with steel balls to crush the ore. The gold, silver and copper that came out of the flotation mill would be bagged and shipped to the smelter.
Later the process was changed to use cyanide to dissolve the gold from the fine crushed rock. Next, the gold-bearing solution is collected. Finally, the gold is precipitated out of solution by adding another metal like zinc. The gold is then collected as a dried paste and shipped to the smelter.
The one thing all these methods had in common was that they were toxic to the environment. The heavy snowfalls and run off leached heavy metals from the tailings piles and the ponds and polluted the streams and rivers around Telluride and Pandora.
William
Edit: Since most mines and mills were located in the high mountains it would have been unusual to have a smelter. Smelters needed a large supply of coal to operate and this wasn't found in the same areas as gold and silver. The smelter at Durango was supplied by the coal mines nearby at Porter and Perrins Peak.
