Minerals

Chemistry in Mining

During Earth Science WeekTM, we went to a lecture by Dr. Innocent Pumure from UCM called “Sonochemical Extraction of Arsenic and Selenium from Pulverized Rocks Associated with Mountaintop Removal Valley Fill (MTR/VF) Method of Coal Mining”.

You may be wondering, what is Mountaintop Removal Valley Fill Mining? First, the excavation company blows up (or strips) the top part of the mountain to remove vegetation and expose the coal seams. The coal seams are then mined through the open cast/strip method, and the extra rock and soil is dumped in nearby valleys called valley fills. It is cheaper and easier to do than regular mining, where they dig a vertical shaft down and do everything through the tunnel, but it blasts the mountain apart and looks ugly. Since 30% of electricity in the USA comes from coal, valley fill mining is still pretty popular.

In 2002, the EPA found too much selenium downstream of a certain mine in West Virginia (we’re not going to say which one). It was over 5 ng/mL, which was the limit back then.[*] 7 years later, there was still an active mine there and the water still had too much selenium. Even worse, the surrounding sediment had 10.7 mg/kg selenium. This could cause problems for the environment later. Due to bioaccumulation, you could say once it’s in there, it’s really in there.

So now we get to the topic of Dr. Pumure’s talk, in which he and his colleagues discovered a way to quickly find out how much selenium and arsenic were in the ground around this mine in West Virginia. When you do a chemical analysis, you usually have to break down the samples in order to measure what is in them. One method to do this would be to take some core samples and do an acid extraction, but that takes a long time and uses a lot of reagents. Sonochemical extraction uses ultrasound energy to accelerate the leaching process that would naturally happen as rocks become weathered. Since it is ultrasound, it does not directly touch the sample, is minimally invasive, and does not need any reagents except water.

Next, he explained the methodology, which means a description of exactly how they did it in the lab: the size of the extraction cells, how much water and power were used (200W/cm3), how long the samples were sonicated, and all the other pertinent information for chemists. Pumure actually spent quite a lot of time finding out the optimal sonicating time to get the best extraction. It turned out the best times for his sample sizes were 20 minutes for Se and 25 minutes for As. That’s really fast![**] Then, he did a comparison to a chemical sequential extraction to make sure that the sonochemical extraction method was getting everything. To summarize, yes it was. Finally, he did a principal component analysis of core samples from different places all over the mountain using this same technique. They found some really interesting trends and correlations, for example, it appears that there is more arsenic in illite clay than other types of clay.

This research has many useful applications. If you were running a mine, you could take samples more frequently to see if your mine is polluting the surrounding environment, and then you could do something about it before the EPA finds out. The method could probably be used for other analytes, too. For other research needs, you could now quickly analyze large batches of mineral samples to get lots of data that would otherwise be too expensive or time consuming to obtain.

[*]The EPA has since lowered the limit and now it is 3.1 ng/mL.
[**]For comparison, some of my colleagues do chemical extractions that take 2 days.
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Extremely Hard Water

A metal pipe completely filled with white gypsum crystals

Steve Hardinger and Dragon Minerals. Retrieved from Mindat Photo of the Day

Everyone knows Kansas City’s water tastes really good, despite being “hard water.” Kansas City municipal water averages 100 ppm (CaCO3 equivalent), which is classified as “moderately hard” by the Water Quality Association. But these people’s hard water would be off the charts!

A valve was stuck in a pipe somewhere in the Naica mining complex in Chihuahua, Mexico. “The valve was removed with the aid of a saw, and voila! the pipe was completely clogged with fine, colorless and gemmy gypsum crystals to 7 cm.”

No word on what they did with the crystals after they unclogged the pipe.

Sources: https://www.mindat.org/photo-773687.html

https://water.usgs.gov/edu/hardness.html

Mozarkite Trip to Lincoln

MOZARKITE, MISSOURI’S STATE STONE by Roger K. Pabian

(Editor’s note: This article was written by Roger and printed in The Gemrock in 2002. It is written about a field trip taken by Roger and Bill and Betty White.)

On May 3, I took a trip to Kansas City and then on to Lincoln, Missouri, to examine the in place occurrence of Mozarkite, the Official State Gemstone of Missouri. As part of my ongoing study of cryptocrystalline and amorphous quartz family gemstones, I thought that the Mozarkite mine would be a worthwhile trip.

In Kansas City, I joined up with Bill and Betty White on Friday afternoon. Bill and I spent much of the afternoon at one of the major tool houses there and I purchased quite a few diamond tools and other tools that would be of use for stone and metal work. We also hit one of the retail salvage outlets, a store that carries distressed merchandise, as they often have many tools of considerable value for very low prices.

On Saturday morning about 7:00 A.M. we left Independence for the small town of Lincoln, Missouri. The town is famous for its annual rock swap in September. There we teamed up with Linville Harms, owner of the Mozarkite mine, and then went on to the mine. The attached photos of the Mozarkite and the Mozarkite mines help you get a better idea of what the site is like.

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Photos by Roger K. Pabian

Mozarkite is not an accepted mineral name but is simply a trade name that was developed to promote the acceptance of the stone as Missouri’s official State Gem and to generate sales to both lapidary and tourists. The name has found acceptance in some circles but is not an acceptable mineral name in others.

Mozarkite has formed in place in marine sedimentary rocks of Ordovician age — it probably is most common in the Jefferson City Formation. The Jefferson City Formation is comprised mostly of dolomite with silty and cherty stringers running through it. There are very few fossils in dolomized rocks as the addition of magnesium to the calcium carbonate of the limestone usually results in complete re-crystallization of the rock and destruction of any fossils or sedimentary structures therein. We did observe a fragment of a brachiopod shell that escaped destruction. It appeared to be a flat-shelled, long-hinge lined form, probably a strophomenoid, but no other determination could be made of it. Much of the local lore about Mozarkite attributes it to igneous activity but there is no evidence for any in that area of Ordovician or younger rocks.

The Mozarkite appears to be of strictly marine sedimentary origin. Some of the nodules show evidence of an accumulation of siliceous gel or ooze on their outer surfaces.

There appears to be three different facies of Mozarkite. The gemmy kind is a dense, brittle form that shows no crystallinity at 10X magnification. A second kind is what the locals call “sugary” Mozarkite. Some of this is quite colorful and has interesting patterns and enjoys some gem use. The “sugary” kind, However, this does not polish nearly as well as the dense, brittle kind. Then, there are some nodules that appear to be very fine sandy textured.

The three facies or textures of Mozarkite suggest that sorting of particles may have been one of the key factors in the origin of the material. Sorting of particles simply means that as some energy form such as wind or flowing water moved a mixture of unconsolidated particles, the heaviest or largest particles are the first ones to drop out of suspension. You can observe this phenomenon on the gravel bars of a stream or in the bars along beaches, estuaries, or lagoons. The coarsest particles will be on the upstream end of the bar or nearer the bottom of the bar. It may well be that the gem Mozarkite is a quartz argillite, a sedimentary rock made up of quartz particles of clay size, that is, smaller than 1/256th of a millimeter. The gemmy facies could also be derived from silica of organic or volcanic origin. The “sugary” facies is made up of the particles larger than 1/16th but smaller than 1/4 mm.

The source for the silica that makes up Mozarkite is currently not known. It may have been from Precambrian granite rocks that are found to the south and east. Sponge spicules may have been the source of silica; I will not totally disregard them. However, I usually favored volcanic ash as the source of siliva for large bodies of chert or flint in marine sedimentary sequences. If there was any volcanic activity involved with Mozarkite, it was from volcanoes that were far away from the Mozarkite-bearing strata.

Mozarkite is a very interesting gem material that could shed a lot of light on the geologic events and processes that led to its formation. My comments above are only a few ideas about its occurrence. Like many other ideas on his stone, my hypotheses need more documentation before they can either be accepted or rejected. My hypotheses should probably read as follows: “Mozarkite is a quartz argillite of marine sedimentary origin that formed in situ in shallow seas of Ordovician age. The source of the quartz is shield rocks of Precambrian ages that lie to the southeast of the area from which it is not found.”

To prove that, several things need to be done. First, properly oriented (top and north) nodules need to be collected from in place in the mine pits. The nodules should not be examined in the field to avoid “high grading” the material. An outcrops map or diagram would need to be made that shows the places from which each nodule was taken. Similar sampling should be carried out from several different layers in several different parts of the mine. The facies of each nodule would need to be located on the map. Does one zone produce only sandy material whereas another produces only gemmy material? Or do these facies occur at random? Thin sections (30 microns) would have to be made. The nature of the particles (angular or rounded) and any cement between them would need to be noted. Is there a silica cement between the particles or does their angularity hold them together? Then other occurrences, both geographic and stratigraphic, of Mozarkite would have to be noted. The sedimentary structures in the Mozarkite and the host rock would also have to be observed and recorded.

By the time all of this is done, one has done enough work to earn a Master of Science Degree. As you see, there is no easy answer for Mozarkite. Perhaps, as a club, or group of clubs, we might think of funding a student to carry out the above kind of research.

mozarkite open pit mine Lincoln Sedalia

Linville Harms (left) of Sedalia, Missouri, and Bill & Betty White examine the open pit mine. Linville is the mine owner. Photo by Roger K. Pabian

 

1917 Geologic Maps

kansas city missouri geologic mapShow-Me Rockhounds member Dan Snow has provided these geologic maps of Kansas City from 1917 which contain topographical, geological, and cross-sectional data. The maps show where to find several different types of rocks common to this area. They are also a great way to see how Jackson County has changed in the last 100 years. The maps are in PDF format and are very high resolution, so please zoom in!

Cross Sections (21 MB)
Jackson County (55 MB)
Kansas City (53 MB)

Cuprosklodowskite

This is from the Musonoi Extension mine, near Kolwezi, Shaba Province, Zaire, from the collection of Michael Scott. The Rruff Project used single-crystal X-ray diffraction to confirm the identity of the cuprosklodowskite. It is basically Sklodowskite (named after Marie Sklodowska Curie) that contains copper.

More info: http://rruff.info/cuprosklodowskite/display=default/

Cave Formations Show Evidence of Fire

stalactites inside a cave

Drip water in Yonderup Cave contains evidence of an aboveground fire. Credit: Andy Baker/U. New South Wales

Stalactites and stalagmites form in caves when water that contains dissolved minerals (such as calcium carbonate) drips from the ceiling. Scientists can analyze the 18O/16O ratios (isotopes of oxygen) in the stalactites and see how the temperature changed as they were formed. A team led by Andy Baker, Gurinder Nagra, and Pauline C. Treble of the University of New South Wales, Australia discovered that Yonderup Cave had a lot more 18O than they expected. Since having more 18O is associated with higher temperatures at the time of formation[1], it could have been interpreded as one of the largest climate changes in the last 2 million years.

But, there was a wildfire in 2005 and a large tree died right on top of the cave. Baker’s team believes that this is what actually caused the increased 18O concentration. This is important for anybody else trying to use these oxygen isotopes to determine ancient temperatures, because if they get a very warm result it might have been caused by a forest fire instead.

[1]It’s a little more complicated than that. Read the whole article here: http://cen.acs.org/articles/94/i30/Cave-dripwater-contain-fire-evidence.html and check Baker’s website for more interesting stuff about how he researches caves to learn about past climates.

Carborundum

iridescent purple and green silicon carbide

In Mark Sherwood’s case at the Spring 2017 show. Photo by Stephanie Reed

At Mark Sherwood’s talk “Earth Science… Facts, Frauds and Scams” he mentioned carborundum (also spelled carborundrum). It is made of silicon carbide, but it is not a natural mineral that you can find in the ground. If you want to find some carborundum, look in a chimney. At an iron foundry, the carbon and silicon in the smoke rise and precipitate on the inside of the chimney. When the chimney is cleaned, they find these nice silicon carbide deposits. They are iridescent and pretty enough to buy, but don’t be fooled. Some sellers will say that carborundrum or moissanite and pretend like it is from some secret mine or even a meteorite, but it is really a man-made mineral.

Note: Moissanite is a naturally occurring silicon carbide, but it is very rare and it doesn’t look like the specimen pictured above. It actually looks like tiny green glass crystals. They are usually heat treated to increase clarity. If so, the seller needs to disclose that the specimen has been heated or they are being fraudulent. Buyer beware.

Spring 2017 Gem Show Photos

The Spring 2017 Gem and Mineral Show was very successful. The parking lot was filled to capacity and we made over $3000 for the scholarship fund. I think it helped that it was so cold on Saturday, because people wanted to do something indoors. Here are some of the highlights.

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My favorite exhibit: The Earth’s Rainbow by Maple Woods Community College. It shows minerals of every color and how they get their colors. Photo by Stephanie Reed

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Geological features of Missouri made out of minerals by Susan Judy (Stone Quilt Design) Unfortunately, it was already sold when I saw it. Photo by Stephanie Reed

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Mr. Bones was wondering what was so interesting on this person’s phone. Photo by Stephanie Reed

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David and Stephanie Reed showing off the new Association banner. Photo by Bob

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Cretaceous fossils from Kansas, displayed by KU. The iridescent baculite is especially nice. Photo by Stephanie Reed

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Selenite crystal from Kansas. I sold it at the Association Booth. Photo by Stephanie Reed

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Shea Oak slab in UMKC’s petrified wood exhibit. This specimen usually lives at the Sutton Museum at UMKC. Photo by Stephanie Reed

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A blue morpho butterfly seen at Butterflies by God. Photo by Stephanie Reed

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The Bead Society had a lot of great cases. Photo by Stephanie Reed

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Keshi pearls (i.e. non-nucleated pearls) from Avian Oasis. Photo by Stephanie Reed

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Jeanna and Jim in foreground, Chet and Bob in background. Photo by Stephanie Reed

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Agatized Dinosaur bone from the Morrison Formation in Utah, seen at Science Leads the Way. We met the person who found it. Photo by Stephanie Reed

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Australian Boulder Opal cabs from Dreaming Down Under. Photo by Stephanie Reed

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This otherworldly glass sculpture was at Madagascar Gemstones. Photo by Stephanie Reed