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Posts Tagged ‘tailings’

Welcome to Eureka sign on U.S. 6

Welcome to Eureka sign on U.S. 6

It’s time to take a break from recounting my tour through Colorado’s mining towns last summer and catch you up on what we’ve been doing this year at Walden School of Liberal Arts.

Maples in the fall near Eureka, Utah - with junipers and rabbit brush.

Maples in the fall near Eureka, Utah – with junipers and rabbit brush.

As mentioned earlier, we received a grant from the American Chemical Society to study lead contamination in the soils in Eureka, Utah and the surrounding area. The grant provided funds for travel, equipment, chemicals, and supplies. It took until early October to receive the money, so our first trip down had to wait until mid-October. It meant we wouldn’t have much daylight, but we’d have to do our best.

Canyon of Fire: Maples in the East Tintic Mountains

Canyon of Fire: Maples in the East Tintic Mountains

I’ve been gradually documenting the history of the area, collecting historical photos, taking photos around the town myself, etc. Back in 2009, I took a group of students with me to interview June McNulty, President of the Tintic Historical Society. He showed us through the museum and we videotaped the tour. Now, with this grant, we can tell the story of recent events in Eureka, especially the history of the EPA superfund project over the last ten years that cleaned up or covered up contaminated soils in the town.

TIntic HIgh School from the Godiva Mine site

TIntic HIgh School from the Godiva Mine site

My science research class researched the history of the area during first term while we were waiting for the grant funds. They identified 20 collection sites outside town using GoogleEarth. Some of these are old mine waste dumps, some are around smelter or concentration plants or leeching piles. Others are control sites outside the district. We were going to collaborate with students at Tintic High School, who were to collect from sites in town. Unfortunately, our collaboration fell through, so my students eventually collected from sites inside the town as well.

Valley of maple trees from a mine dump in the East Tintic Mountains

Valley of maple trees from a mine dump in the East Tintic Mountains

In preparation for our sample collection trips, I traveled down to the area to get some photos of fall foliage on Saturday, Sept. 22. I got there just at the right time, when the maples in the canyons were at their brightest. I photographed some areas along Highway 6 leading into town and filmed the maples in the canyons along the road leading over the top to Dividend. I then took videos around town by attaching a Flip camera to my left rearview mirror with a small claw-style tripod. I drove up to the Godiva mine site and took photos down toward the high school, then drove further up the canyon past the Knightsville site and hiked around some mine dumps further up. I had seen that there was a valley nestled inside the East Tintic Mountains from GoogleEarth and my 3D models of the area. There was a road leading along the edge of the hills, and I walked around as far as the site of the Iron Blossom #2 mine. The headframe there has recently collapsed. It was a nice trip and the photos turned out well. I also saw and photographed several deer.

Doe a Deer: A mule deer  doe in the East Tintic Mountains

Doe a Deer: A mule deer doe in the East Tintic Mountains

Ruins of the Irom Blossom #2 Headframe

Ruins of the Irom Blossom #2 Headframe

I took four students to the area on Oct. 19 and we collected samples and explored the area, including the road over Silver Pass. We first collected from some old evaporation ponds near Elberta where hot water pumped out from the Burgin mines was allowed to cool and settle before discharging it into Utah Lake. During the early 1980s, as I drove home from college to my hometown of Deseret, I would pass through this area and see the water steaming as it passed down the gulley to the ponds. This was the last time they had attempted to open the mines at Burgin. We sampled from two locations inside the old ponds, which can be reached by a short walk from Highway 6.

Collecting samples at the settling ponds near Elberta

Collecting samples at the settling ponds near Elberta

We then collected from the bottom of the wash at the mouth of the canyon leading up to Burgin. The soil here looked healthy and contained a combination of sand and humus. We then stopped at the old Burgin concentrator and took some pictures. I talked with the men at the main office of the Chief Consolidated Mine operations there about getting some samples from the tailings piles (they corrected me when I mentioned “tailings piles” around the headframes themselves and said those rocks were more properly called mine dumps or waste rock; tailings are the actual ore that has been processed).

Silver ore concentration plant at the Burgin mine

Silver ore concentration plant at the Burgin mine

We took photos around the Trixie headframe, then drove on up the canyon over the top of Silver Pass, which I had not done before. This was the opening of the deer hunt, so I didn’t want to venture too far from the road without orange clothing.

Headframe at the Trixie Mine above Burgin.

Headframe at the Trixie Mine above Burgin.

We also collected at a mine dump next to the road in Ruby Hollow, which I later identified as the Tesora Mine. The soil there had a bright yellow color and contained obvious sulfides. Part of the shaft is still there without much protection around it.

Collecting samples at the Tesora Mine dump in Ruby Gulch

Collecting samples at the Tesora Mine dump in Ruby Gulch

I also showed the students Silver City, the leeching pile from the 1980s when much of the waste rock and tailings were heaped up and cyanide solution was sprayed onto it, chelating the silver and gold out of the rocks. We stopped at the Bullion Beck headframe for photos and walked around the Tintic Mining Museum. It was late afternoon by then and time to get the students back.

Waste rock pile at the Swansea Consolidated Mine near Silver City

Waste rock pile at the Swansea Consolidated Mine near Silver City

Altogether we collected six samples from three sites and the students had a chance to get to know the area. I knew that we would have to be more productive on our next trips. Back at school, we did some simple pH tests and found the first two sites (Elberta Ponds and Burgin Wash) were near neutral pH, but the Tesora Mine samples were quite acidic, at a pH of about 3.5. Other tests would have to wait until we ordered the testing supplies.

Historic churches in Eureka, Utah.

Historic churches in Eureka, Utah.

Belt-driven drill press at the Tintic Mining Museum

Belt-driven drill press at the Tintic Mining Museum

Downtown Eureka, Utah: 2012Belt-driven drill press at the Tintic Mining Museum

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mining terms

Mining terminology, at the Creede Underground Mining Museum

As mentioned in my last post, I am embarking on a two-week tour of Colorado mining towns. Before I go, there are some basic mining terms that any greenhorn or tenderfoot like me should know before venturing into a mine. Many of these terms come from the Cornish miners who came to America to work when the tin mines in Cornwall played out in the 1800’s.

First, the basic parts of a mine: you always refer to a mine as if you are facing into it. The part of the mine you are working to drill, load, and blast is called the “face.” The left-side wall is the “left rib” and the right-side wall is the “right rib.” The ceiling is the “back” and the floor is the “foot.” The back is also called the “hanging wall” and the floor the “foot wall” depending on the orientation of the ore vein.

Ore body diagram

Diagram of the original ore body.

A “tunnel” is horizontal and must see daylight at both ends. If it only opens to the outside on one end, it is called an “adit.” If it doesn’t connect to the outside at all, it is a “level.” Levels are like the various floors of a building, only underground in a mine, and they provide access to the ore body. A vertical hole that connects with the surface is a “shaft.” If it is a hole that is dug down from a level or an adit, it is a “winze,” and if it is dug upward it is a “raise.” A hole dug to follow a vein horizontally away from a level or an adit is called a “drift” and to dig out a large ore body going up or down is called a “stope.”

The valuable mineral that you are trying to dig out is the “ore,” along with useless rock called “tailings.” Usually the ore is injected as a hydrothermal body along a fault or other natural zone of weakness in the rock, and the entire mineralized zone is called the “ore body” or “lode.” If it is found as a large vertical mass with branches, it is an “ore chimney” and if it is a thin line following any direction it is a “vein.” Sometimes ore is found as crystals deposited along the walls of a natural chamber. This is called a “vug.” When a vein reaches the surface, it is an “outcrop,” and when parts of the outcrop erode away and are carried down into river valleys by water, avalanches, and gravity it will pile up in still areas of the stream, such as the inner parts of meanders along with gravel. These are called “placer” deposits (pronounced “plah-cer” and not “play-cer”).

exploratory mining

Prospectors mine the placers and conduct exploratory mining

The first miners in a new mining district are prospectors, because they are looking to find, develop, and sell a good “prospect.” Typically the first discoveries are placer deposits, because they are easy to find and work using pans, rockers, and sluices. Once the placers are played out, the prospectors head upslope to find the source outcroppings, or the “Mother Lode.” Once they find evidence of ore (such as associated minerals like iron pyrite or chalcopyrite, quartz, etc.) they will “stake a claim” by pounding stakes in the corners of the land and starting to dig exploratory shafts or adits using hand tools such as picks and shovels. They will use a windlass to haul the “muck” or loose rock out of a developing shaft with a bucket. Claims have to be an allowed size (a long, thin swath of land) and registered in the county mine office to be legal. It’s good to set up with a partner so that when one of you leaves to register a claim, the other can guard it from “claim jumpers.”

Samples of the ore are taken to an “assay” office where they are analyzed chemically to see how much valuable metals are actually in the ore. If the ore is rich, or “high grade” or if the vein widens and appears to continue, the prospector will usually sell out to a mining company with the resources and capital needed to further develop the mine.

Once the mining company buys out the prospectors, it starts to build the infrastructure needed to enlarge the mine. The irregular prospector shafts and adits are enlarged and shored up with timbers. The top of a shaft is boxed in with a “collar” and an adit’s entrance is shored up and extended outward to prevent loose rock from falling into it. This becomes a “portal.” At the top of a shaft, a “headframe” or “gallows frame” is erected out of large timbers or steel with pulleys called “sheave wheels” at the top. A braided rope or cable is brought over the sheave wheel and attached to a metal cage called a “skip” which can carry men or ore buckets in and out of the shaft. The other end of the cable is brought to a “hoist,” which is an electric or diesel winch. As the skip is raised and lowered in the mine, a series of electric bell chimes are used to signal the “hoistman” how far to raise and lower the skip. A mark on the cable tells the hoistman when the skip is “on the level.”

mine expands

After a mining company buys the prospect, it expands the mine and adds infrastructure

As the mine deepens, it will usually encounter underground aquifers or water tables which become a major problem as they start to flood the lower mine shafts. The main shaft must be dug lower than the lowest level and a pump installed to remove the water. This low-lying shaft is called a “sump” and the pumps used ran on steam, diesel, electricity, or compressed air. The biggest of these were the famous Cornish pumps found in some mines.

Eventually the shafts are too deep to economically raise all ore cars, sump water, and men to the top of the shaft. A drainage and ore removal adit is sometimes dug at the bottom of the mine that will drain out the waste water and allow easy passage of ore cars out of the side of the mountain. These adits usually have a slight downward slope to the outside so the loaded ore cars can be more easily moved. Waste rock was simply dumped out of the shaft or portal and created a “tailings pile” downslope from the mine or mill.

integrated mine

Integrated mine and mill. As the mine develops, drainage adits, interior shafts, reduction mills, smelters, and other structures are built.

As the mine gets bigger, with additional levels every 100 feet and a complex set of drifts, adits, winzes, raises, interior shafts, stopes, etc. it becomes advantageous for the owners to build their own mill instead of sending their ore elsewhere for processing. A mill is built on the side of the mountain below the lowest portal. It first sorts, then pulverizes the ore into powder, then concentrates the ore mechanically or chemically. The concentrate is then shipped by rail to a smelter for final processing and purification. Sometimes the concentrated ore is heated in a retort or furnace but not separated into its final constituent metals. This combination of metals is poured into bar-shaped or cone-shaped molds and cooled, creating “dore bars” or “buttons” which contain gold, silver, and other metals.

Once the mine is exhausted of ore, or the shaft extends down below where it can be economically drained of groundwater, or the price of the final metal drops so the mine can no longer turn a profit, it is closed down (sometimes temporarily). Today, mines have to post bonds that force them to reclaim the mine and make it safe once mining has concluded. But in the old west, the mines simply shut down and left everything where it was. Tailings piles are the most obvious evidence of mining, and the rocks are often stained a yellow, orange, or reddish brown color from iron sulfides and sulfates. Rotting timbers poke from the ground, and rusted metal scraps adorn the slopes. Drainage water still seeps from adits, often contaminated with metals or other effluents. And the shafts and portals remain, too often a temptation for the unwise to explore. A few people die each year from cave ins while exploring old mines, or get killed by handling old dynamite left in mines. In some states, such as Utah, a concerted effort is underway to close all of these abandoned mines in the name of public safety but at the expense of history. Other states, such as Colorado, seem to strike a better balance between history and safety.

Mining terms B

More mining vocabulary terms. From the Creede Underground Mining Museum.

Now there are many more terms, such as how a typical miner spends his shift to drill, load, shoot, and muck the face. We’ll talk about these later as they come up on my journey. I’m amazed at how many mining terms have made it into general vocabulary, such as “big shot” [blasting out a large section of the face], “hang-up” [when ore is blasted to fall into a lower chute but gets stuck], “getting the shaft” [to buy a worthless mine], etc. For better or worse, hard-rock mining has had a big impact on our history and our culture.

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