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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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For the last week, I’ve been busy preparing for my classes at Walden School, including inventorying the science lab room (which is also my classroom) and planning out my course schedules. I’ll be teaching two sections of Chemistry, one of Astronomy, one of Computer Technology (a basic computer literacy course required in Utah), a section of Media Design, and a section of Video Production. This is, for me, a perfect schedule. In the meantime I’ve also been preparing a series of maps and 3D images of the Tintic Mining District, focusing on the ore deposits and the various mines located there. I’ve also prepared the script for this section of the video, which I have pasted below:

Mines in the East Tintic Mts

MInes and Roads in the East Tintic Mtns.

Tintic Geology

To understand how the ore bodies in the Tintic District were deposited, we have to start about 800 million years ago in the Precambrian Period when the western portion of the North American craton rifted away from the rest of the continent along a line where the Wasatch Front now lies – this Wasatch Line has been an important hinge line in Utah’s geology ever since. For the next 600 million years, a sequence of ocean sediments including dolomite, limestone, shale, and sandstone were deposited off the coast in the geosyncline that would become western Utah. Beginning 150 million years ago, Nevada and then western Utah were uplifted as the Farallon tectonic plate was pushed under North America. Like a throw rug being wrinkled up as it’s pushed over a hardwood floor, western Utah was folded by thrust faults into a large mountain range during the Sevier orogeny about 70 million years ago. This thrusting continued across eastern Utah and into Colorado and Wyoming during the Laramide orogeny, building up the Uintah and Rocky Mountains.

East Tintic Mines

Mines in the eastern portion of the Tintic Mining District

Then, about 50 million years ago, the Farallon plate began to collapse from underneath the continent. As it peeled away, a wave of volcanism moved from east to west across Colorado and Utah. Intrusive laccoliths rose to the surface, bulging up the LaSal and Henry Mountains in eastern Utah and forming explosive calderas in several places in western Utah. About 35 million years ago, a series of calderas formed in the area that would become the Tintic Mountains. A large andesitic volcano rose up from eruptions of ash and tuft.

Tintic Standard ore samples

Ore samples from the Tintic Standard Mine, eastern district.

About 31.5 million years ago, the volcano collapsed as the intrusive magma began to cool. Mineral rich fluids were injected into the surrounding limestone, quartzite, and dolomite as replacement beds. The hot magma caused the carbonate rocks to decompose; for example, limestone turns into lime or calcium oxide and carbon dioxide gas when heated. This left large cavities that then filled up with the mineral-laden magmas. These deposits are called stopes, such as the famous Oklahoma stope of the Chief Consolidated mine. The carbon dioxide released from the decomposing limestone and dolomite in turn dissolved into the hot magma, making it a kind of lava champagne, and reacting with it to form various exotic minerals, some of which are found nowhere else.

More Tintic ore samples

More ore samples from the Tintic District

The primary ore-bearing minerals in the Tintic District are enargite, tetrahedrite, galena, sphalerite, pyrite, marcasite, and native gold, silver, and copper. But many more minerals are present, including unusual minerals that blend copper, silver, tellurium, arsenic, sulfur, carbonates, hydrodixes, etc. At the Centennial Eureka mine, over 85 different minerals have been identified, ranging from common pyrite, malachite, and azurite to minerals found only here. It is the type locality (where the mineral was first identified) for leisingite, frankhawthorneite, jensenite, juabite, utahite, and eurekadumpite. Other rare minerals include xocomecatlite, carmenite, adamite, duftite, and mcalpineite.

These mineral deposits occurred around the edges of the caldera and formed the five large ore zones of the main Tintic District. The Gemini Ore Zone runs to the west of Eureka south to the north edge of Mammoth Gulch. The Gemini, the Bullion Beck and Champion, the Eureka Hill, and the Centennial Eureka mines (known collectively as the Big Four) are located on this zone.

The Chief-Mammoth Ore Zone begins under the center of Eureka and extends due south across the mountain to the east end of Mammoth Gulch. The Chief Consolidated mine is located on the richest ore body, which is right under the center of Eureka city; up the hill is the Eagle and Blue Bell mine, named for the beautiful deposits of azurite found inside. Further south over the top of Eureka Peak lie the Grand Central, Mammoth, Apex, and Gold Chain mines that are also part of this deposit.

Ore zones in the Tintic District

Ore Zones and Major Mines of the Tintic Mining District

The Plutus Zone branches off of the Chief-Mammoth Zone high up in the Tintic Mountains. The Godiva Zone starts just east of Eureka and runs southeast in a curve where it joins the Iron Blossom Zone, which continues in a curve south and then southwest. Some mines in these zones include the Godiva, May Day, Humbug, Beck Tunnel, Sioux, and Iron Blossom mines.

In the eastern section of the Tintic District, several zones of minerals were deposited and were among the last to be discovered because they are overlain by 400 feet of igneous rock. These bodies include the Burgin ore body, the Tintic Standard, and the North Lily bodies. Other bodies are located at the Apex and Trixie mines.

In the southern section of the Tintic District, the large replacement bodies give way to smaller fissure veins that are only two feet wide on average but can be up to 4000 feet long. Here, the mineral-bearing magma was injected into cracks and fault lines already existing in the host rocks. The Dragon mine is the only true open pit mine in the area; it sits on top of a network of fissure veins at the south end of the Iron Blossom Zone. Other mines in the area include the Swansea and Sunbeam mines at Silver City, the Tesora and Treasure Hill mines at Ruby Gulch, and the Showers mine at Diamond Gulch.

More ore samples from the Tintic Standard Mine

More ore samples from the Tintic Standard Mine

The final chapter in the area’s geomorphology began about 17 million years ago when normal faulting created the Basin and Range province, lifting up blocks to form the mountain ranges of Utah and Nevada, including the East Tintic Mountains. Other blocks sank to form the valleys, such as the Tintic Valley. Erosion has exposed the ore bodies in many places, including the outcropping that George Rust stumbled over in 1869. It was to become the Sunbeam Mine.

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