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Some of the soil samples from the Tintic Mining District

Some of the soil samples from the Tintic Mining District

Although it’s been over six months since we conducted these experiments, I want to report on what we did before moving on to other topics so that these blog posts will be in the right order. So much has happened doing chemistry that I’ve fallen behind on reporting and writing about chemistry and the elements.

Chemistry students test chemicals with the ALTA II reflectance spectrometer

Chemistry students test chemicals with the ALTA II reflectance spectrometer

During our Intersession class in March, we visited the Tintic Mining District three times in addition to our visit the previous fall. This made four collection trips altogether, and we got 42 samples from over 20 locations. Some of these were from areas inside the town of Eureka, some were outside in areas with heavy mining, such as on or around mine dumps, and some were control samples where no mining has occurred. Our goal was to test these samples for lead and other metal contaminants as well as pH.

Sean, Jem, Indi, and Jeffrey add water to soil samples

Sean, Jem, Indi, and Jeffrey add water to soil samples

We did this in several ways. First, we took a field pH meter with us to test the soils as we collected the samples. Since most were gathered in March, the ground was damp and the pH meter worked well. The areas around mine dumps showed extremely low pHs (the meter pegged at about 2.5, so the samples were lower still). They also showed the most discoloration, ranging from yellow to purplish colors. These sites also had little or no vegetation.

Chemicals and minerals tested by the chemistry students using an ALTA II reflectance spectrometer

Chemicals and minerals tested by the chemistry students using an ALTA II reflectance spectrometer

Measuring pH using universal test strips

Measuring pH using universal test strips

Even though the field pH meter worked well, we weren’t sure if it was consistent or reliable given that the soil samples had different amounts of moisture. When we took the samples back to our chemistry lab, we took them out of the Ziploc bags they were in and placed them onto paper plates to dry for several days. Students measured 10.0 g of each and added 25 mL of distilled water, stirring the samples to mix the soil with the water as much as possible. Then we tested each with the pH meter, universal pH test strips, and more specific test strips. We also used a garden soil nutrient test kit that included a pH test where a pill was emptied into the wet sample and color read off of a chart. The various results were set up on the whiteboard as a table, then my student Jem set up a spreadsheet to record and chart all the samples to compare which pH test method was most sensitive and accurate.

Testing for lead with sodium rhodinzonate. The blue color of the second to last sample indicates both lead and acid.

Testing for lead with sodium rhodinzonate. The blue color of the second to last sample indicates both lead and acid.

Another test was to see how much lead was in the samples. Our technique was to use a kit for testing lead in soils using a solution of sodium rhodizonate, which turns from reddish orange to pink in a control solution of lead nitrate. Our samples brought back from our first and second collect trips were tested by filtering out the sediment from the soil mixed with water, then taking the filtrate and adding the rhodizonate solution. Most of the solutions stayed orange, but one turned purplish blue, not pink. It was the sample taken from the Tesora mine dump. This was puzzling until one of my students, Sean, looked up the rhodizonate test and found that it does turn purple-blue if the sample is acidic. When testing its pH, we found it was highly acidic with a pH of 3.0.

Results of rhodizonate test, with colors ranging from orange (no lead) through yellow (moderate lead) to green and blue (high lead). The test was qualitative, not quantitative.

Results of rhodizonate test, with colors ranging from orange (no lead) through yellow (moderate lead) to green and blue (high lead). The test was qualitative, not quantitative.

We began to see there was a correlation between low pH and lead content. As we repeated the test with other samples, we refined our techniques and came up with a color gauge that provided a rough quantitative scale for the amount of lead present. Most samples, including all from inside town, had a pH of 6.5-7.0 and the rhodizonate stayed orange. Where the pH was a little lower (6.0-6.5 and 5.0-6.0), such as in areas downstream for mine dumps, the rhodizonate turned orange-yellow or yellow. A pH of 4.0 – 5.0 showed a rhodizonate test of light green. A pH lower than 4 showed a test of blue. The correlations between the amount of lead and the acidity of the soil were very strong. We set up a scale of orange equals no to very little lead, yellow a small amount of lead, green a larger amount, and blue the largest amount with numbers 0 to 4. Unfortunately, the rhodizonate test is not specific enough to show actual quantities of lead, and we have no way of knowing if a number 4 (blue) test has twice as much lead as a number 2 (yellow) test. That will have to wait for x-ray fluorescence spectroscopy or some other technique.

Control tests using the sodium rhodizonate solution (on the right). The second to the right shows pink color when the test solution is added to a neutral solution of lead nitrate. It turns purple (second from left) in an acidic solution that contains lead. It produces a white precipitate in a solution basic solution of lead. In the soil samples, lead in acidic soil produced a blue color. When a base was added, a black precipitate formed. All samples with lead present were also highly acidic.

Control tests for lead using the sodium rhodizonate solution (on the right). The second to the right shows pink color when the test solution is added to a neutral solution of lead nitrate. It turns purple (second from left) in an acidic solution that contains lead. It produces a white precipitate in a basic solution of lead. In the soil samples, lead in acidic soil produced a blue color. When a base was added, a black precipitate formed. All samples with lead present were also highly acidic.

We also tested for soil nutrients, including phosphate, nitrate, and potassium. The only correlation was that the soils with higher levels of lead had higher potassium levels overall, but the correlation wasn’t completely certain.

Sean tests for nitrogen in the samples

Sean tests for nitrogen in the samples

I had seen an interesting device demonstrated at a workshop for the landing of the Curiosity rover on Mars where we used reflectance spectroscopy to analyze rock samples representing Martian rock analogs. The ALTA II device uses 11 LED lights on the bottom to shine off of a rock or mineral sample, then a detector shows the relative reflectance of each wavelength, ranging from blue through red to four frequencies of infrared LEDs. Using a white paper and a black paper as controls, the percent of reflected light can be determined and charted. Before Intersession began, I had the chemistry students use the ALTA on a series of chemicals. Some were white but of different substances, some were pure elements, such as copper, tin, lead, iron, and sulfur. Others were alloys such as bronze or compounds such as copper sulfate or minerals such as iron pyrite. I wanted to see if the alloys were an average between the pure elements that made them up, and to see if the infrared reflectance was different even though the visible colors of substances were white.

Reflectance spectrometer readings for various chemicals and minerals. There are 11 wavelengths read for each sample, which are compared to the values for white and black to get a percent reflectance.

Reflectance spectrometer readings for various chemicals and minerals. There are 11 wavelengths read for each sample, which are compared to the values for white and black to get a percent reflectance.

We also used the ALTA on each of the soil samples, and the results were fairly predictable in that the richer, loamier soils had lower reflectance at all frequencies (they are darker). The more mineralized and contaminated soils were lighter (more yellowish overall) and high reflectance. Yet the yellow soil didn’t necessarily have higher yellow reflectance – it might have higher green and red, which were combining to make yellow. This spectrometer isn’t specific enough to really give detailed reflection spectrums, which would show spikes at specific frequencies for lead or other elements.

Recording data for the reflectance spectrometer on the Tintic soil samples.

Recording data for the reflectance spectrometer on the Tintic soil samples.

Doing 11 wavelengths of light for 42 samples created a huge data table. We also had all the nutrient, pH, and lead data. Jem set it all up in a massive spreadsheet. Our ten-day class finished before we had the chance to analyze the samples from our final collection trip, so another student, Jeffrey, continued to work on the samples on his own time. By the end of the school year the results were all finalized. I’ll talk about those results in my next post.

Jem enters all the data into a spreadsheet.

Jem enters all the data into a spreadsheet.

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Replacing topsoil Eureka Utah

Replacing topsoil in Eureka, Utah

On my visit to the area around Eureka, Utah last Friday, June 4, I not only wanted to visit Mammoth and Silver City, but to also document the efforts by the Environmental Protection Agency to clean up the town. I had traveled through Eureka a few days before on Memorial Day and noticed that the lawn and soil around the LDS chapel in Eureka was being dug up to a depth of about 18 inches. On Friday, crews were in the process of bringing in new soil in dump trucks and spreading it over a layer of black plastic where the lawns used to be. Normally I wouldn’t have noticed it much – just chalked it up to them putting in a new sprinkler system or something similar. But I knew differently. This was the latest site in an ongoing process to replace the topsoil throughout the entire town, which is a huge undertaking. All the old mine sites throughout the district have left a legacy of environmental contamination and pose a danger to careless explorers who try to enter mine shafts or tunnels or ruins.

Ore dump at Dividend

Ore dump at Dividend, Utah

When silver ore was discovered in the East Tintic Mountains by George Rush in 1869, it ignited a stampede of mining claims that spread throughout these mountains. New deposits were soon located and claimed, and the ore was assayed to be rich in silver, gold, lead, zinc, copper, and other minerals, usually in the form of metal sulfides. The most level sites near the mines quickly grew into the towns of Eureka, Mammoth, Silver City, Diamond, Knightsville, Dividend, etc. These towns were usually as close to the mines as possible so the miners didn’t have far to walk, so that miner’s houses and the mine buildings, hoists, smelters, railroad depots, and city businesses all competed for space in the narrow canyons. Tailings dumps of discarded minerals and slag from the smelters covered the hillsides around and above the town. Dust from these piles was blown by the frequent winds (this is western Utah, after all) and blanketed the whole town. Nobody thought much of it at the time. It was all just part of life in a mining town. But the entire topsoil was contaminated with lead and other metals down to about two feet under the surface.

Limestone rip-rap in Eureka

Limestone rip-rap covering a slope in Eureka, Utah

Downtown Eureka with limestone rocks

Clean-up operations near downtown Eureka, Utah

Today, the EPA has identified the area around Eureka as a SuperFund site, spending millions of federal dollars to clean up the contamination.  One by one, the yards of the residents and businesses are being dug up and the soil replaced, brought in from a staging area east of town. To prevent the tailings piles from blowing more toxic dust around the town, broken limestone rocks called rip-rap are being hauled in from a nearby quarry and are carefully placed to cover over the tailings piles to prevent further erosion by wind and water.

Mine dump in Tintic Mts.

Mine dump in East Tintic Mtns.

The work is progressing throughout Eureka, but the entire mining district has the same problem. Recent exploratory work has dug up the tailings piles in Silver City again, leaving the yellowish sulfides once again exposed to erosion. Many of the mine sites in the hills are owned by small-time private owners who keep the mines open on an occasional basis. They don’t have the resources to prevent the erosion of their tailings piles, and much of the East Tintic Mountains is contaminated just as Eureka itself is.

Old mine shaft

Abandoned mine shaft at Dividend, Utah

Another problem in the area is the many abandoned mine tunnels and shafts. Mines today are required to provide reclamation funds before the mine can even open, but it wasn’t an issue in the 1800s and early 1900s when most of these mines were active. The owners took the ore from the hills, then left all the scars, holes, pits, slag, tailings, and buildings behind when the ore ran out and their companies closed. Now these ruins are a hazard to casual explorers; every year or two someone dies falling down an abandoned mine shaft in Utah. The state has begun a program to close off these mines; to place grates or metal doors in the tunnels and shafts or to blast the entrances closed. Over 8000 mine sites have been closed off throughout the state through this program, but many, many more remain to be done.

Knight Smelter at Silver City

Ruins of the Knight Smelter at Silver City, Utah

Smelting or concentrating the ore brought its own environmental problems. Jesse Knight, the silver magnate that started Knightsville just southeast of Eureka, also built a smelter at Silver City in the early 1900s that operated for about eight years. The foundations of this smelter still remain, as do residual chemicals used to concentrate the ore, including mercury. When I visited the site on Friday, I found a man and his two young girls exploring the site. I suggested that he wash off his girls’ hands and shoes carefully once they were done because the whole site is contaminated with mercury (June McNulty, who runs the Tintic Mining Museum in Eureka, told me that he used to play with pools of liquid mercury metal that would seep into pockets around the smelter).

Knight Smelter

Remains of the Knight Smelter at Silver City, Utah

Right to the south of the old smelter lies a large heap of grayish tailings, now slowing growing a crown of weeds and grass. All the tailings left from the Knight mill were scooped up in the 1980s and placed on a pad with drainage pipes running through the pile, then a solution of cyanide was pumped and sprayed over the pile, leaching its way down through the tailings and chelating with the remaining gold and silver. The ore from these mines has been worked and reworked to get every last fraction of value out of it. But now the pile has been left just like all the other piles around, but with the addition of cyanide. I don’t know if steps have been taken to reclaim the pile, but I wouldn’t want to walk around on it.

Leaching pile at Silver City

Cyanide leaching pile at Silver City, Utah

The efforts to clean up these environmental messes is necessary, but it does come at a cost beyond just money. To clean up the town and make it safe to live in, its essential history and character has been changed.  The heavy equipment moving in limestone and soil has shaken apart a number of fragile historical structures, including buildings, homes, and headframes. Where there were colorful tailings piles slowly returning to nature, there are now carefully constructed fresh piles of gray limestone rocks, an ideal hideout and breeding ground for rattlesnakes (no joke here – I ran over one in my minivan as I was driving up the road to Mammoth). Eureka doesn’t look the same as it did ten years ago.

One can argue that Eureka must be dynamic and capable of changing. It’s not a museum but a living town, and change is part of life. But the historian in me hates to see history destroyed in the process. That is one of the main reasons I’ve started the Elements Unearthed Project and have traveled to Eureka several times in the last few years with my cameras and equipment; as the EPA clean up progresses, the town is changing and I want to preserve what can be preserved of the history before it’s gone forever.

Tailings piles at Silver City

Erosion of tailings piles at Silver City, Utah

The beryllium video second half is progressing well. I’ve decided to do the three episodes on the TIntic Mining Districts next instead of blown glass because It’s fresh on my mind and I now have all the footage and photos I’ll need. My goal is to get the beryllium video done and uploaded by the end of this week, then the Tintic videos by mid-July. Then I’ll start hitting the streets looking for financial sponsorship to continue this project.

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