Video
The Kennecott Mill
Transcript
At the beginning of the 20th century, the world was hungry for copper. Copper was essential for building ships, locomotives, and automobiles. Every home needed copper pipes. Electricity was the energy of the future, and copper wire was the key to bringing electricity to the world. In 1900, two prospectors discovered the richest deposit of copper ore left in the American West. The copper was on a steep, rocky peak surrounded by rivers of ice in the heart of the Alaskan wilderness. This region of Alaska is now known as Wrangell-St. Elias National Park and Preserve. The exceptional richness of the copper ore shocked the mining world. Typically, copper ore contains 10% copper. This ore contained as much as 85% copper. Two wealthy industrial investors made a bold plan to mine the copper. The JP Morgan and Guggenheim families pool their resources and form the Kennecott Mines Company, named after the glacier next to the copper load. They faced extraordinary challenges. How would they get the copper from the steep, snowy mountaintop, transport it across 200 miles of gravel-covered glaciers and steep mountain passes? Would it be possible to work through long Alaskan winters with 50 below zero temperatures and relentless snow? And the biggest question of all, would the endeavor be a success or a financial failure? Between 1905 and 1911, the company built a 200-mile railroad connecting the mines to the nearest seaports. Crews had to build 30 miles of trestles to raise the tracks over rugged terrain. Every piece of material used in construction had to be brought in by a combination of steamships and sleds pulled by dogs or horses. To get around river rapids, workers dismantled entire steamships, brought them over the mountains, and reassembled them on the other side. The Kennecott Mines Company also organized a steamship line to bring the copper from the Alaska coast to a smelter in Tacoma, Washington. At the top of the copper field ridge, miners blasted five mines and connected them with 70 miles of tunnels. [MUSIC PLAYING] They built three miles of aerial trams to bring the copper down from the mountain. The mining town of Kennecott sprouted up and would eventually support 20 families and hundreds of workers. The Kennecott Mines Company had to contend with one final challenge. The copper coming down the trams was mixed in with limestone, which had no value. A typical piece of ore coming down the tram might have contained 40% copper and 60% limestone. Moving the rock by train and steamship was expensive, and the company couldn't afford to ship the limestone along with the copper. They had to devise a way of separating the copper from the limestone. For this, a 14-story concentration mill that's still towers over the town of Kennecott. The mill is a maze chutes, ladders, and mysterious machinery. It's full of winding catwalks and creaky floorboards. If you look hard enough, you can still piece together the story of what used to happen inside the mill. OK, we're here at the bottom of the jumbo tramway, which brought ore down to the mill from the jumbo mine. Cars containing, oh, 250, 300 pounds of ore would come down on this cable and then break loose and go onto an overhead track. At this time now, muscle power takes over until we're ready to go. Your tram operator is pushing the car through and taking it over to the crushers. The mill had four basic parts. The top part of the mill was for crushing and separating the rock. The second part was for concentrating the copper. The third and fourth sections were for extracting the copper through leaching and flotation. The milling began with crushing. First thing you need to do is to reduce the material to a size that you can work with it. It's already been broken twice up in the mine, once when it's blasted loose from the face, and then once through a crusher before it goes into tramway cars. Now, when it gets here, it goes to the primary crusher for the mill, the jaw crusher, where we're going to make it smaller once again. This first crusher broke the rock into pieces the size of marbles. Some of these pieces had high levels of copper. Workers picked out these high-grade pieces and sent them down a chute that went directly from the top of the mill down to the train. The rest of the ore went through giant rolling sieves that separated the sandy gravel from the larger pieces of rock. The larger pieces went on to more crushers until all of the material was sandy gravel. This sandy gravel moved into the second part of the mill, which was the concentration section. Here, the mill took advantage of the fact that copper is heavier than limestone. The mill had rooms full of gravity concentration tables that separated the two kinds of rock by weight. It has a slight tilt towards that end. It also has a slight tilt that way towards away from the feed side. Ore, which is called pulp in this case, a mixture of rock and water, comes into this large box and spills out through the back side across the table. Process water comes in through this small box, flows down along the channel here, and we adjust the flow with these diamonds so that it comes evenly across the back side and goes across the table. Now, when ore is coming in, the table is bouncing back and forth. The ore is bouncing up and down. The water is flowing this way. Light materials, waste materials bounce higher. The small, heavy ore particles can't climb over more than one or two or perhaps three of these ripples, so we get a dark streak here, which is a high grade, which falls off that end of the table. We get a light white streak, which is the limestone, which is waste, goes across the table that way. The dark, rich ore from these tables washed into giant settling tanks. From there, the ore was placed into sacks for the train. Now, the way it works is I take a jute bag, which is all dusty and everything, but it would have been then too, fit it onto the machine. This bar holds it in place. Then I pull this lever, which opens the chute, fills the bag, and I shut it off. Now, if I've got too much, I got a mess to clean up. So I release the bag, tie it up, and let it slide out onto the track, out onto the railroad car. The waste rock from the concentration tables was sent on for further processing. Most of this rock was sent to the third part of the mill, which was the leaching section. We've left the concentrator behind, and we've crossed over into what is called the leaching plant. Now, over here, chemistry and science solves a specific problem, what to do with all the waste that looks like this stuff, except it's full of copper. The gravel was poured into giant leaching tanks and then covered with ammonia. The ammonia dissolved the copper out of the limestone, and once again, the copper ore was sacked and put on the trains. Some of the ore that came off of the concentration tables was too small to be sent through this leaching process. This sandy ore was sent straight from the tables to the fourth section of the mill, which was the flotation section. Here, copper could be extracted from even the tiniest piece of powdery sand. This tank and many more like it back that way are filled with eucalyptus oil. And you have air bubbling up through it. The oil forms a bubble, a sheen around the bubble, and the finely ground copper ore sticks to the bubble and comes up and forms a froth on top. It almost looks like whipped cream, except it's gray and ugly. And you have paddles that then beat it off the sides. It falls into a trough, slides down into a drying area, and then you sack it, put it on the train. And like everything else, it eventually goes to Tacoma. Through all of these steps of crushing and concentrating, leaching and flotation, the mill extracted 98% of the copper that came down from the mines. This is considered good, even by today's standards using modern technology. One of the most amazing aspects of the Kennecott operation was that it functioned 363 days of the year. Workers managed to keep the trains and trams running months of below zero temperatures and deep, immobilizing snow. The mines ended up producing $100 million in profit before the ore vein ran out in 1938. The Kennecott Mines Company used this phenomenal profit to purchase more copper mines in the Southwest United States. It went on to become the nation's largest copper company and an international force in the metals market. Once the ore ran out, Kennecott was quickly abandoned. Only the most expensive items were taken out by train. Everything else, from dining tables to tram cars, was left behind. Over the years, Kennecott became a popular tourist destination. It was a place where people could step back in time and experience part of Alaska's wild frontier. In 1986, Kennecott was recognized as a national historic landmark. In 1998, the National Park Service acquired significant buildings in the town of Kennecott and 2,800 acres of the surrounding mining plain. The Park Service is now working with other partners in preservation to stabilize the mill and many other main buildings. Today, Kennecott continues to attract visitors from around the world. They come to see the breathtaking beauty of peace and glaciers that dwarf the town. They come to marvel over how such an elaborate operation came to exist in such a remote wilderness. Kennecott tells a remarkable story of human perseverance and of how a nation hungry for copper went to incredible lengths to get it.
Descriptive Transcript
WRST Kennecott Mill Audio Description text
Text, The Kennecott Mill
Copper coins fall into a large copper kettle.
A large sailing ship
An early model car.
A crowded street car
Two men outside a tent in the woods
The mountain range
Green ore
Men in suits at a large table
A snowy mountain
Horses
Train tracks under construction
A man, dog and sled in snow
A boat on a river
Steamships at a dock
Wires up a mountain
Men work in the mine
A town at the mountain base.
Workers outside the mine
The hillside mill
Logan Davis, Mining Historian
An illustration
At the top of the chute
Ammonia Leaching
Animation
The mill, town, train tracks
Heavy snow
A worker pulls a lever at the mine
Tracks in an uninhabited town
Two men in front of a Kennecott building
The town in daylight
Mountains through a window
A miner in the snow.
Credits, Produced by Kristin Ramsey. Narrated by Peter Mayfield. Special thanks to the National Archives and Records Administration and The Peggy Guggenheim Collection.
Description
Discover the processes involved in obtaining, concentrating, and shipping rich copper ore out of the Alaskan Wilderness in the early 1900s at the Kennecott Mines near McCarthy.
Duration
12 minutes, 13 seconds
Credit
Wrangell-St. Elias National Park and Preserve
Date Created
08/15/2018
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