2017 Mining History Association

 

ON THE WAY TO THE MHA...
A Visit to the
Kennecott Mines
National Historic Landmark,
Wrangell-St. Elias National Park
And Preserve, McCarthy, Alaska
June 10-14, 2017

 

Johnny and Dawn Johnsson
Dick And Elna Hauck

PHOTO GALLERY 4 OF 6


Narrative Continued from Gallery 3
 

Then we got into multiple floors of shaking tables, featuring Wilfley, Plat-O, and James Tables, more than 40 in all.  Each section treated or retreated a grade and size of feed or middlings for further classification and separation.  I even saw a Deister nameplate on a table, which is not indicated in the HABS flowsheet.  We did not see the ball mill and some of the other equipment listed on the flowsheet.  Several classifiers were in this section as well.  A Dorr Thickener in the lower section was pretty impressive.  Below this were concentrates storage, handling, bagging, and loading systems.

 

Many modifications were made to the mill before it closed down in 1938.  By WWI, the bottom end of the mill was being modified to prepare 8% copper feed for an ammonia leaching circuit built downhill of the main mill across the railroad tracks and main street.  In the 1920s froth flotation was added as well.   Both the ammonia leach and flotation mills buildings are closed to public viewing, so the tour is mainly the gravity concentration portion.  Scattered throughout the town is a patchwork of private property/dwellings/buildings in various states of use/repair that people bought between 1938 when the town shut down and today.

 

Narrative Continues on Gallery 5


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Coarse ore that had passed over the screens was routed through the Traylor roll crusher and recirculated back to the vibrating screens.

Hancock jigs shown above and Harz jigs were used as the first stage of concentration of the undersized material from the screens.



(Above)  Large areas inside the Mill were used for several stages of shaking/concentration tables.  The tables were of various designs from several manufacturers.  Wilfley tables are shown above.

 

(Right)  Visitors on the Mill Tour pass through one of the floors of concentration tables.

 




(Above)  The Nameplate on a Deister table.

 

(Right)  The drive mechanism of a Deister table controlled the shaking action.

 

(Above) The concentrating table surface was usually covered with linoleum.  As the slurry of ore particles passed over the oscillating table surface, the heavy copper mineral particles were trapped behind the wooden riffles and moved toward the end of the table.  Dick and Elna (right) are observing the details.

 

 (Right) Plat-O tables were used to recover valuable ore concentrate from slimes (very fine particles).  The nameplate is on the drive mechanism.


A Mill section using James Simplex tables.  A ball mill (not accessible on the tour) was used to regrind ore for greater recovery of small mineral particles.


A Dorr thickener was used to dewater process slurries.

Dawn Johnsson is standing in the concentrate bagging area.


Copper River & Northwestern Railroad cars were loaded from ore bins and loading docks at the bottom of the Mill.


Two of the most striking features of the Kennecott Mill are the long exterior stairways. It is difficult to imagine anyone climbing them in the Alaska winter.  They may have been once enclosed.  The chutes for passing the hand-picked, high-grade, direct shipping ore to the rail load-out followed a similar path as the stairways.
 

This view from the Mill shows the roofs of the Ammonia Leaching Plant (ca1916-1918) and the Flotation Plant (ca1923) building directly below the roofline of the Mill. These processes were the final two stages of ore concentration at Kennecott.  The combined moraine from the Kennicott and Root Glaciers is shown behind the Ammonia Plant.
 

 Although no photo was taken of the Ammonia Leaching and Flotation Plants during our 2017 visit, this view from the 1986 HABS/HAER documentation file shows their building with the Mill in the background. Some metallurgists consider the ammonia leach process the most important technological innovation developed at Kennecott.
(Photo courtesy Library of Congress)
 

Photos by Johnny and Dawn ohnsson


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