North London Mine and Mill History
Compiled by Kate McCoy, PhD
NoLo Executive Co-Director
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| North London Mill Site, between 1893 and 1897. Courtesy Bob Shoppe |
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| Photo Courtesy Park County Office of Historic Preservation |
The London Mines and Mills were reported in local news outlets as integral to the economy of Park County as an employer and purchaser of supplies. Further, the financial and managerial ups and downs of the operation are emblematic of the challenges of gold mining. Foul play, ignorance, incompetence, and under-capitalization plagued mining and milling operations of the nineteenth and early twentieth centuries. The London was no exception.
The North London Mill was one of the largest mills in Park County, but was fraught with difficulties in efficient recovery of metals from the ore it processed. This resulted in nearly continuous changes to the mill equipment and the processes used until, finally, a flotation mill was installed. This rapid change in equipment and technologies is of historical interest and importance. The physical characteristics of the mill with numerous machinery mounts and other features demonstrate the complexity of the problems the mill operators faced.
1892, Fairplay Flume:
The London has had a checkered career, having in ten years suffered serious depreciation through mismanagement and incompetency. Good authorities estimate that at least $500,000 has been squandered by superintendents who knew nothing about the best method of handling the peculiar class of ore found in the workings.
In 1912, Horace Bushnell Patton and co-authors of the report Geology and Ore Deposits of the Alma District, Park County, Colorado noted the challenges of mining in the Alma District:
The prospectors of this area have always been more or less seriously hampered by a lack of rational knowledge of the geology. This drawback was accentuated by the peculiar complexity of the prevailing, typical formations, which feature is brought out in other chapters. This complexity, taken in conjunction with the further peculiar circumstance that some of the very different rocks present a striking similarity, may be taken to account for a vast amount of hard prospect work done in formations that, from the scientific viewpoint, offered no warrant. Much time, effort and cash has thus been really wasted; but the expenditure was made in good faith by all concerned.
North London Mill Operation
1892-1894: Stamp Mill--Stamps were heavy iron blocks or cylinders controlled by a cam device. As a stream of water washed the ore under the stamps, the heavy blocks crushed the ore to a sandy-like consistency to free the gold. The water then washed the sand into a trough or over copper plates generally embedded with mercury via capillary action. The mercury caught and held the gold in an amalgam. Workers then scraped off the amalgam, sent it to a retort, and there recovered the gold and the mercury. The waste product of the process was called tailing or tailings, deposited in what was called a tailings pond or pile nearby and left to dry.
At the North London Mill, ore was crushed in two sets of rolls, one of which was 3 ft. in diameter, and passed through sizers on its way to six jigs where lead was recovered. Next, the ore passed through a battery of 40 stamps set up in eight groups of five stamps from where the resulting slurry flowed over amalgamating tables where free gold was recovered. Slimes that passed over the tables were conveyed to bumping tables for further recovery of gold. Motive power for the mill was an 80-horsepower boiler that operated a steam engine; coal for the boiler was held in a coal shed with an 80-ton capacity.
Capacity of the mill was initially reported to be 100 tons per day, but this was quickly downgraded to 60 tons per day and then 50 tons per day, perhaps because of difficulties in having the mill efficiently extract the minerals in the ore. In December 1892, it was reported that each of the stamp batteries had two Joplin jigs as companion pieces of equipment, perhaps an early installation of new equipment to improve the mill’s performance. The report also identified the bumper tables below the amalgamation plates as Gilpin County tables from which concentrates were recovered (Fairplay Flume, June 16, 1892:4, June 23, 1892:4 and September 8, 1892:4; Leadville Daily/Evening Chronicle, December 8, 1892:1 and April 17, 1893:2).
1897: Copeland Process conversion to cyanide plant?
In a cyanide plant, various devices crushed the ore into a very fine consistency, then water carried the sands into cyanide vats. There, the gold dissolved into solution, which was then run off, and then precipitated out through the use of zinc shavings.
The London has had a checkered career, having in ten years suffered serious depreciation through mismanagement and incompetency. Good authorities estimate that at least $500,000 has been squandered by superintendents who knew nothing about the best method of handling the peculiar class of ore found in the workings.
In 1912, Horace Bushnell Patton and co-authors of the report Geology and Ore Deposits of the Alma District, Park County, Colorado noted the challenges of mining in the Alma District:
The prospectors of this area have always been more or less seriously hampered by a lack of rational knowledge of the geology. This drawback was accentuated by the peculiar complexity of the prevailing, typical formations, which feature is brought out in other chapters. This complexity, taken in conjunction with the further peculiar circumstance that some of the very different rocks present a striking similarity, may be taken to account for a vast amount of hard prospect work done in formations that, from the scientific viewpoint, offered no warrant. Much time, effort and cash has thus been really wasted; but the expenditure was made in good faith by all concerned.
North London Mill Operation
1892-1894: Stamp Mill--Stamps were heavy iron blocks or cylinders controlled by a cam device. As a stream of water washed the ore under the stamps, the heavy blocks crushed the ore to a sandy-like consistency to free the gold. The water then washed the sand into a trough or over copper plates generally embedded with mercury via capillary action. The mercury caught and held the gold in an amalgam. Workers then scraped off the amalgam, sent it to a retort, and there recovered the gold and the mercury. The waste product of the process was called tailing or tailings, deposited in what was called a tailings pond or pile nearby and left to dry.
At the North London Mill, ore was crushed in two sets of rolls, one of which was 3 ft. in diameter, and passed through sizers on its way to six jigs where lead was recovered. Next, the ore passed through a battery of 40 stamps set up in eight groups of five stamps from where the resulting slurry flowed over amalgamating tables where free gold was recovered. Slimes that passed over the tables were conveyed to bumping tables for further recovery of gold. Motive power for the mill was an 80-horsepower boiler that operated a steam engine; coal for the boiler was held in a coal shed with an 80-ton capacity.
Capacity of the mill was initially reported to be 100 tons per day, but this was quickly downgraded to 60 tons per day and then 50 tons per day, perhaps because of difficulties in having the mill efficiently extract the minerals in the ore. In December 1892, it was reported that each of the stamp batteries had two Joplin jigs as companion pieces of equipment, perhaps an early installation of new equipment to improve the mill’s performance. The report also identified the bumper tables below the amalgamation plates as Gilpin County tables from which concentrates were recovered (Fairplay Flume, June 16, 1892:4, June 23, 1892:4 and September 8, 1892:4; Leadville Daily/Evening Chronicle, December 8, 1892:1 and April 17, 1893:2).
1897: Copeland Process conversion to cyanide plant?
In a cyanide plant, various devices crushed the ore into a very fine consistency, then water carried the sands into cyanide vats. There, the gold dissolved into solution, which was then run off, and then precipitated out through the use of zinc shavings.
1915: Cyanide unit installed
1919: Mill operated with two crushers, 20 stamps, a ball mill, and a cyanide plant with a capacity of 50 tons per day.
1927: Mill converted to flotation plant.
In a flotation plant, material is ground very finely to free the minerals present and then agitated with saponifying agents–i.e., soap–the sulfides and other minerals adhered to the soap bubbles and rose to the water surface generally as dark gray bubbles. From here, the bubbles could be run off, the water evaporated, and the minerals recovered for further processing. [Process developed by Carrie Everson, a nurse in Denver, for her husband’s mines. She didn’t get credit for this work.]
At the North London Mill, ore delivered to the mill from the tramway emptied into a 300-ton ore bin with an automatic feed to a Marcy ball mill. Crushed ore then passed through a trammel screen with fine material passing over a roughing table. Oversize material and material exiting the roughing table passed through a Dorr classifier, which returned coarse material back into the crushing circuit. Finely crushed material then entered Devereaux conditioning tanks and entered Fahrenwald and Brown pneumatic flotation machines. Tailings from the flotation machines were then passed over pilot tables. The separated concentrates from the flotation machines were dewatered by cone classifiers and filters then deposited in settling tanks from where they were packaged for delivery to the American Smelting and Refining Company (ASARCO) smelter in Leadville. Uneconomic tailings were sent to impoundment ponds southeast of the mill. The reconfiguring of the mill reportedly increased its capacity to 100 tons of ore per day.
1938: Mill possibly converted to grate-type, low discharge plant. (Could not find much information. Seems to be sophisticated crushing and sorting machinery that does not use much water or chemicals.)
North London Mine and Mill Timeline
1873
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Ore bodies discovered
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1876
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Ore bodies surveyed—Mother, Paris, London, and Hard to Beat lodes
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1878
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Lodes patented
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1879
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Sheriff’s sale notice—windmill, three cabins, equipment
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1879-1880
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Enormous windmill (60 ft arms) at the site built to power drills. Blown down by January 1880
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1881-1883
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London, South Park, and Leadville RR spur off the Denver, South Park and Pacific Railroad line to the terminus of the North London Hallidie 3300 ft tramway,
reportedly first of its kind in Colorado. Ore taken to mill at London Junction (junction of Route 9 and CR 12); office and boarding house also built at this time. The mine headquarters in Fairplay was connected by telephone to the the mill at London Junction, the lower ore house, and the mine. |
1884
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Mine closed due to legal disputes over ownership and financial problems; Sheriff sale notices
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1885
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Mine reopens. Railroad spur foreclosed and taken over by South Park and Leadville Short Line Railroad Company
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1888-1891
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Mine and Mill at London Junction closed. Mill inefficient.
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1892
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North London Mill built at North London site by Hendy & Meyer Engineering Company directed by D.A. Byers, including new tramway feeding directly into the mill.
Grading done by A.L. Peterson. An electric generating plant was included for lighting the mine and mill. |
1893
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Mineral survey for the Joe Dandy Lode and the London Mill Site March 31, 1893 (show plat)
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1897
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Copeland Process machinery installed in mill (converting it to a cyanide plant?); mill shut down in December 1897 due to lack of water; mine and mill
leased by John M. Kuhn |
1899
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More repairs made to the mill; railroad to the mill ceased operations
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1902-1912
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Mine and mill shut down, by 1912 the property was falling into ruin; operations shifted to the South London Mine
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1914-1922
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North London property operated by London Mines and Milling Company, managed by Charles P. Aicher
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1915
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Mine and mill leased to John Nelson, who reportedly installed a cyanide unit.
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1923
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London Mining and Leasing Company takes over lease
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1927
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Cyanide plant removed and mill converted into a flotation plant, reportedly the first in the Alma district.
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1930
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Electricity added to the mill from power lines
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1935-1937
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North London Mine and Mill leased to Fairplay Gold Mines Company, the Brisco brothers
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1938
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London Mines and Milling Company possibly converts mill to a grate-type, low discharge mill?
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1939
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London Mines and Milling Company liquidates stock, some sources indicate that the operations ceased at this time, but photographs from the Denver Public Library
archives show women working in a mill in 1942, with captions indicating the North London Mill |
Link to the:
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| Original 1893 Mineral Plat of the North London Mill Site |
by
Jonathon C. Horn
Principal Investigator
Alpine Archaeological Consultants, Inc.
P.O. Box 2075
Montrose, Colorado 81402-2075
Prepared for
North London Mill Preservation, Inc.
PO Box 380
Alma, Colorado 80420
September 2017
Prepared for
North London Mill Preservation, Inc.
PO Box 380
Alma, Colorado 80420
September 2017