To Death Valley or Not to Death Valley

Warning: not amateur science. This one is more like, what I did this weekend for fun.

Recently we made the move from Idaho to Nevada. Part of the tradeoff from the move included the ability to drive from the relatively high elevation cold temperature basin and range country to the lowest spot in the country, Death Valley, within a few hours. As the forecast for this weekend included snow at the new home in Nevada, I thought to take advantage of the nice weather I expected at -200 ft elevation of Standpipe Wells.

The drive from our neck of the woods to Death Valley involves a relatively uneventful trip south through Tonopah and then Beatty Nevada. This is the southern edge of the Nevada basin and range where the topography makes the transition to more subdued alluvial fill basins separating widely spaced mountains. The total elevation drop is something like 6700 feet in a three and a half hour drive. The majority of the drop is in the final thirty miles out of Beatty and down the mountain range into Death Valley. My ears popped the entire way down.

Yawning and chewing gum on the Daylight Pass road into Death Valley, the basin opens up with a wide view of Standpipe Wells to the southwest and Furnace Creek to the south. The mountains to each side are rich in complex structural geology, including on peak to the north that is suffuciently faulted to be called Corkscrew Peak. The road comes over the pass onto a steep alluvial fan, maybe a six percent grade. Large boulders litter the slope at the top of the fan and grades to smaller and smaller rock as you drive toward the valley basin. Occasional monolithic outcrops emerge from the smooth alluvial fan, very out of place blocks rotating out from the faulted basin fringes. The driver slows down to a turtles pace to navigate the road placed in a channel eroded from just such a block called Mud Canyon.

The road makes an unnecessarily complex set of turns that allows you to head north to Scotty's castle, south to Furnace creek or continue west to Stovepipe Wells.

Stovepipe Wells is a little outpost composed of a motel, gas station, campground and ranger station. The last time we visited, we stayed the night at the motel. As with any national park hotel it was insanely overpriced and provide an adequate living space. In late October, when the rest of the country is facing the pre-Halloween blizzard, Stovepipe Wells is the perfect temperature. There is little better than waking up at seven am to find the sun edging over the surrounding mountains casting the entire valley in the soft glow of the dawn magic hour.

Right down the road there is a dirt road forging up the alluvial fan to the south toward the base of the towering Tucki Mountain. The gravel parking lot at the top of the road is at the outlet of Mosaic Canyon. When I visited there was blue skies with a hint of black storm cloud sending feelers over the top of the mountain and a whole parking lot full of cars. Now Mosaic Canyon is one of those amazing little features that funnels an entire mountain range's worth of runoff through a two foot wide and twenty foot deep canyon...maybe once or twice a year when the rain comes. My concern at the time was that the rain clouds that were ominously rumbling up at the peak of the mountain were preparing to send a wave of water, trees, rocks and tourists down the trail at me.

The geology of the canyon was great. The reason folks go to Mosaic Canyon is because of the butter smooth marble walls of the lower canyon. The marble is truly beautiful with alternating bands of orange, cream, and dark brown - if it weren't in a national park, they would be making counters from the stuff. The periodic water and gravel abrasions scalloped and ground the marble to the point where it became "soft" as a youngster exclaimed as he slid down one of the walls. The good stuff was all within a quarter mile of the parking lot.

The marble is not the only interesting geology. There was a fine grained matrix supported coarse, angular clast conglomerate that could be found at the upper contact of the marble, although it could also have been lithified alluvium or possibly volcanoclastic. Large pumice boulders were occasionally sticking out of the canyon wall above the marble. Higher up the canyon mineralized ironstones and quartz laden metasedimentary rocks litterered the canyon floor. The slopes lining the canyon walls were red metasedimentary rocks and looked mineralized but I did not see evidence of mining. The canyon became unaccessible about a mile up from the parking lot at a steep cliff that would have been a challenge to free climb.

 

The next destination was to find a camp site and maybe check out some of the old mining that happened at Death Valley. Continuing on the road going west from Standpipe Wells, the highway skirts an alluvial fan gaining elevation quickly until it is a bit above two thousand feet at Emigrant, a campground and rest stop. From there, take the Emmigrant Canyon Road and follow it, gaining elevation the entire way. At one point the foundation of an old mill appears on the south side of the road and the gravel road to Skidoo is about a mile later.

The gravel road to Skidoo is a winding, clothes washed rutted, and occasionally blasted from a sheer cliff face. A few miles from the road entrance the telltale piles of rock betray the presence of mining. Some of the infrastructure has even been preserved by the park staff. This small head frame still has the sixty foot shaft is still open and timber supported with a serviceable ladder. The entrance itself had been blocked by a cable mesh rock bolted to the shaft walls.

A number of exploration holes were present and curiously followed a outcrop of a quartz vein in the granite bedrock. A little shack was built on the other side of the valley. The mineralization I could find in the piles were open vein fill crystals of some white mineral that had a botryoidal habit. There were small yellow sulfide crystals mixed in, possibly pyrite or tetrahedrite and a dark accessory mineral in the white quartz veins. It looked a lot like the gold vein I found with a metal detctor in Quartzite a few years back.

Continuing down the road, I discovered the town of Skidoo, an old mining town at the top of the world above the Death Valley. There was a sign marking the site and hundreds of mine workings in the surrounding hills. All the buildings had been removed and there was no visible evidence that the place had once been home to dozens of large buildings less than one hundred years ago. The sign did have a few black and white pictures of the valley from the the towns heyday. Investigation of the quite large workings in the granite nearby showed backfilled trenches or gated adits.

Here is a nice one pager website on Skidoo.

I ended up camping nearby that was certainly not in the posted "Day use only: No camping" area. I set up our large family tent on a roughly flat area before the looming clouds and dark arrived. Between the elevation and oncoming storm it became quite cold. Despite the four season tent and Idaho-class cold weather gear I ended up having a bad night. The wind blew the tent down, although to be fair, the water stayed mostly outside.

When the sun finally came over the horizon it was still raining and gusty. I managed to stuff the sleeping gear and muddy tent into the back of the jeep and get off the mountain before the rain turned to snow. The bad weather really put a damper on the plan to hike out to some of the more remote mine workings.

On the way out I snapped a picture of the Mesquite Flats Sand Dunes during the rain and it can be compared to the picture I took a few months ago when the weather was ideal.

Normal

 

With Rain

Death Valley is a great place when the weather is nice. I hope to get back there one of these upcoming weekends when the weather improves but before it gets too hot later this spring. I love the idea of being able to drive out of the bad weather. It didn't work out this time but I am hopefull that it will work sometime in the future.

That's one small step for man, one giant leap for robotic lunar mining-kind - Part 2 Exploration

Exploration is crucial for any mining operation, including one on the moon. In this case I use the term exploration as a mining term which includes activities that determine whether or not a mineral or element is present in a prospective mining area. But I think anyone would agree that all places on the moon are not made equal when it comes to mining. Take, for example, that the moon has a surface area a little bit smaller than that of the Continent of Asia. Do you think that I could start a mine anywhere in Asia and find what I am looking for?

There needs to be some way to narrow down the possibilities when selecting the site. A few givens will be obvious immediately, especially if we are looking for water. If water is the target mineral, there are a only few large craters at the northern and southern hemisphere that are shadowed all year long. But, if we are hunting for helium-3 or metals or sulfur, we need to do something to figure out where there is more..say, sulfur, and make a plan to go there. In this case, I want to use sulfur for the remainder of this discussion because it seems to have the most practical use as a cement in a type of lunar concrete that has been proposed.

The Exploration Geologist on Earth has a number of tools in his bag. He usually starts with a series of maps that help him narrow down what likely geologic structures might have concentrated the minerals of interest and whether that particular unit occurs in one spot or extensively. Aerial photographs are often used for this purpose initially. Then as targets are developed, multispectral spectrographic imagery could be used to look for telltale signatures of the presence of a particular mineral or element (depending on the technique). Additionally both types of maps could help him determine if there are helpful outcrops that he could go and sample to verify.

Where would we find such maps of the moon? All the results from the 1994 Clementine mission, which includes UV to visible and Infrared Images are available online for any interested parties. http://www.lpi.usra.edu/lunar/tools/clementine/  Also, the more recent Lunar Reconnaissance Orbiter has a suite of instruments that can detect and map any number of minerals that could be used to narrow down a mining target.  http://lunar.gsfc.nasa.gov/index.html The limitations are numerous and could include the specific element of interest (Clementine looks like there are 5 spectral bands available, which is quite limiting) and the pixel resolution of the instrument itself – some of the data is only available on the kilometer scale resolution, much larger than a pit-type mine could be.  The LRO has a much better camera that has imaged tracks and equipment left behind from the Apollo missions. This scale and wider are useful for mining applications.

As a starting point, these satellite images of the moon would be used to determine areas with the highest concentrations of the ore of interest. The preliminary results of the mapping could be used to estimate a volume of ore present in the target location if some work was done in advance to calibrate the spectra to a given mineral concentration.  

The next step would be to get boots on the ground and begin sampling to verify the results of the spectral mineral map. In this particular case we could get lucky and find that one of the Apollo missions sampled material that happened to be spectrally very similar and use the samples that they collected as a type of verification. Alternatively, the meteorite bombardment that pulverized and mixed the upper layer of the moon, the regolith, could be so well mixed that there is not enough variation to be picky. In this case, any target area with a sufficiently deep and extensive regolith could be adequate. However, the odds are that the people who are doing the mining are going to want to optimize their mining by finding a location with even incrementally better concentrations of sulfur. And the only way to verify that is by getting on the ground and developing a sampling plan.

Sampling is a surprisingly complicated subject. In the easiest case, you have a guy who walks around with a shovel and bags and a map and picks up samples roughly evenly distributed across the target area. However, there is a dark and sullied corner of science that deals with how many samples are statistically required to get a representative understanding of the material present.  The statistics are driven by the extent of the ore body, the structural limits of the ore body, the consistency of the sample results, the magnitude of the sample results, the sensitivity of instrument measuring the ore concentration, and any secondary elements that could mask the presence of the ore, among others. Reading through this list it is easy to see that planning for the correct number, spacing, and depth of samples requires knowledge of the ore body that a geologist may not have until after the sampling has started. This puts the geologist in charge of the budget in an odd spot where planning for the adequate amount of data may not be possible without clairvoyance or a good deal with the devil. In this case it is always good to make a facts-based estimate for the number of samples and then double it.

Another kicker is precisely how we sample. There are a couple different methods that immediately come to mind. We have already discussed the idea of taking a shovel and filling a bag. There are also small tools to core out shallow boreholes from soft material such as regolith. And then there are the big boys, using a drilling rig to collect a deep continuous sample of core or chips.

Here is a cartoon of a layer of ore-bearing regolith sitting above a layer of barren regolith. The ore is concentrated on the top by, say, cosmogenic processes – solar wind has been enriching the upper foot of regolith with He3 for the past billion years with little interruption.  Each type of sample is shown, a small shovel excavation, a deep shovel excavation, a small borehole and a deep borehole. The benefit to a shovel excavation is that it is quick and easy, but the results can be misleading since it is artificially sampling the upper volume of the layer more than the base and so the results would have a somewhat higher concentration bias. The deep shovel excavation results would dilute the concentration by introducing the barren regolith beneath. The small borehole provides an evenly distributed sample that looks to be ideal for this application. Deep drilling would not be necessary for sampling a shallow ore body. The appropriateness of these sampling methods is largely dependent on the type of deposit that exists and removing bias can be a process that takes time and planning and often, can’t be perfected until after mining has begun.

The results of this sampling plan would then be turned into a map that shows the concentration of the mineral or element present at each sampling location. The maps could be contoured or used in a mine modeling program that extrapolates the results between boreholes to try and better determine the extent of the deposit. Once a sampling plan is completed, the concentration and total extent of the ore is defined, and then the first stages of mining are ready to begin.

They don't us Lunatics for nothing

In researching the next post I found this website, www.moonmining.com Pure Gold...er, I suppose that's Pure Moon Dust for the rest of us. Or "Lunar Regolith" for the "scientists" amongst us.

http://www.moonminer.com/Lunar_regolith.html

I have to admire what he has done here. In the introduction he states that "There are no definite processes for extracting metals and gasses from the regolith to be found." I think he is largely correct on that point, but that is where we part ways. The remaining five hundred pages of text are a lot of crazy speculation on blue sky magical thinking about how the human race can eventually reach the stars. The moonmining website is a bit like the goatee-wearing mirror of my whitepaper in the evil anti-universe. This topic deserves an experienced hand and consideration of the technology and resources that could make mining on the moon a reality if enough support ever made it a priority.

The author of this website could, in fact, be the same guy I met at the party in California. I don't know. In all honesty, I will, in fact, be using the references that this author has so diligently researched in advance of my efforts.  

Here is another great idea that I love. At the Lunar and Planetary Science Conference Fries and Steele from the Carnegie Institute propose sending a rover to the moon with a raman spectrometer to look for meteorite fragments in the regolith.

www.lpi.usra.edu/meetings/LEA/.../FriesMDF_Lunar_wksp_07.pdf  Warning! PDF

This harkens back to brief but exciting days of my most recent graduate school field work using a portable handheld raman spectrometer to analyze carbonates in the Mojave desert.The absolutely best part of this abstract is that they named the probe Moonraker. Ala James Bond. Brilliant! The next space instrument I dream up to send to Mars shall be called Goldeneye!

That's one small step for man, one giant leap for robotic lunar mining-kind - Part I Introduction

This is the first of a series of posts where I intend to explore the technical hurdles of mining on the Moon. It is also a living document, like a ball of clay that might need to be reworked until it is just the right consistency to begin pottery. As such, I ultimately want to get this collection of posts into a form that could be published as a whitepaper for lunar mining. It might not be the only solution, but I would like this to be thorough enough to work if implemented.

I met a guy at a party in California during my intern years at Ames Research Center in the summer of 2003. This guy had kind of long shaggy graying hair and sort of dirty clothes and smelled strongly of coffee and cigarettes from a full arms length away. I remember wondering at the time what he was doing there and if he had just wandered in to the gathering from off the street. When I introduced myself he reciprocated and told me he was working on first principles analysis of going back to the Moon. He told me it was his goal to develop an entirely new way of looking at both traveling to and staying at the Moon and that involved retasking and reusing equipment, getting creative with ways to travel on the surface and ways to exploit the Moon's resources once we got there. There are going to be rovers built from spare parts that roll over any obstacle on the Moon’s surface and they will be modular so they fit together to make a habitable base. We will mine the surface not just for the helium-3 that can be shipped back to earth to pay for the operation, but the regolith will also be processed for all the building materials and life-giving elements that a colony needs. This vision of colonization of the Moon was entirely unlike anything that happened during the Apollo mission. It was a vision of sustainably living on the Moon’s surface with a minimum amount of resupply or support from Earth.

This chance meeting has stuck with me ever since largely because it was surprising that this crazy, homeless man had a good enough story to fit in with the rest of us at the party but also because he was right. The next time the human race goes to the Moon, it should be to stay and it should look dramatically different than the first time - the next effort should not be “flags and footprints” so much as dust, sweat and tears.  

Living off the land is the Zubrinian mantra (from The Case for Mars) for how to make sustainable exploration work. In long term economic exploration of the Moon mining is going to be an important part of making the effort worthwhile. One of the previous topics I have mentioned is using a unique formulation of concrete for construction on the Moon. This would require developing a way to mine and purify sulfur before any construction can begin. A different, more popular idea is paying for the missions by mining for helium-3, an isotope that is rare on the Earth, but relatively abundant on the Moon’s surface and can be used to dramatically improve nuclear power production using fusion. I have also heard arguments for mining metal from a thin layer of cosmogenically altered rock on the surface, oxygen bound in the minerals that compose the surface rocks, and silica in that same rock for solar panel production. Mining will also probably be required to extract and purify cometary water from the ever-dark craters that have preserved the ice on the north and south poles. I am going to discuss mining on the surface of the Moon in general terms because it encompasses all of these options. Going down into the depths of the Moon is a different story for a different day.  

There are a few key questions that must be answered before going forward. First, is mining possible on the Moon’s surface? Second, if so, is it more economical than shipping every pound of oxygen, water, food, and construction materials required to sustain life from the Earth? There are likely a wide range of viewpoints that exist varying from yes to no for each question. I think the task of mining on the Moon’s surface is possible, but that it is a much more complicated task than any NASA scientist has ever considered and that could mean that mining and processing is not an economical alternative to flying every piece of a habitable base to the Moon…at least for the forseeable future.

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Mining is a process

In the old days it was drill, blast, muck, haul. Over and over again, as fast as possible. In recent times, the process is basically the same, but with a few extra steps along the way. And I am convinced that the process is the same here as it would be anywhere else materials must be extracted. The big differences are in the details of the individual steps of the process. 


Today mining has two essential tracks, operations and engineering. Operations could occur without engineering but at the risk of long term disaster and failure of the mining operation itself. Each track has tasks that begin with defining an ore body during exploration and go through the steps of mining and processing that ore until it can be milled and a final product is produced. In this case operations includes both the mining and the milling staff.  As the mine progresses the engineering and operations groups work together to optimize the mining operation. This is true for precious metal mines, coal mines, iron mines, and aggregate mines. Below I have a rough diagram that outlines the critical steps for a mine process that would result in, say, sulfur production.

This is a lot of steps and there are very specific pieces of equipment that are used for each step. For example, a medium sized gold mine might have thirty large dump trucks and three or four pieces of loading equipment to extract enough ore to feed a mill and haul waste to dumps. The mill for a mine that size will have a footprint of several acres and be many stories tall with an electrical consumption equivalent to a moderately large neighborhood. The total gold production that might come from such an operation after a full year of production could be shipped out in one armored van.  

How does this analogy transfer to the Moon? Does each step require a crew and equipment or can they be combined into one super miner/miller machine that does the job with an operator or a robot at the controls?

In the movie Moon, Sam Bell, played by Sam Rockwell, is a one-man crew living on a lunar base outpost mining helium-3. His mining equipment are house sized rovers that traverse the surface scooping up regolith and milling it onboard. The shipments of helium-3 are rocketed back to Earth in small containers that are easily manhandled by a single person, surprisingly similar to the gold mine scenario discussed above.  

There is video of this miner in operation at IMDB here http://www.imdb.com/video/imdb/vi1306264089/ Moon 2009 is definitely worth watching, I highly recommend it. You can catch the full show on Netflix streaming or buy it on Amazon.com.   

I love this vision of mining. It is the right idea for surface mining in loose, fine grained material that is rich in ore close to the surface. Instead of taking a block of material by scooping it into trucks that haul it to a mill, it shaves off the upper foot or so, separating the big rocks and hurling them away while processing the good stuff on the inside and dumping all the waste rock out the back.

A scenario like this might actually work for mining helium-3 or water from the regolith. There are plenty of designs for continuous mining equipment that can slowly move across a flat, ripped surface and load the dirt via conveyor to a waiting truck. 

Photo from http://www.ene.ttu.ee/maeinstituut/publications/Development_Valgma.htm

It is not difficult to imagine adding a module that heats up the ore regolith to a temperature high enough to drive off a significant fraction of the helium-3 or water and collect it in some kind of a condenser.  The remaining waste rock is simply cast aside. This idea works because helium and water are relatively volatile and simply warming up the rock is enough to collect it.

 But what about sulfur, or metals, or silica that are bound much more tightly to the rock and require significantly greater temperatures to be liberated? Sulfur is more volatile than the others. If the grains of sulfides (the class of mineral that sulfur would exist in basalt type rocks on the moon) could be exposed in the ore by crushing the rock to the grain-size of its constituent minerals, then the sulfides could be concentrated and heated up and exposed to a reducing agent to react with the metal in the sulfide. On Earth, carbon in the form of coal is added to the fiery mix to drive off the sulfur as a sulfur oxide gas. I am not sure what chemistry could be done using the materials on the moon to make that reaction go – it is unclear if heat alone is enough to drive the reaction.  

That is it for today. We looked at the mine as a process and speculated a little about the validity of some recent science fiction that seems closest to the mark. The next post is going to focus on the first stages of exploration and sampling that will be required in order to define an area that can be mined.   

Concrete in SPACE!

Concrete is awesome stuff.  If there was one thing I wish I had studied more as an undergraduate, it was concrete. Now concrete is used everywhere here on earth, but is it a suitable material for construction on the Moon? A relatively new study looks at that possibility and that paper is summarized in the New Scientist. http://www.newscientist.com/article/dn14977-astronauts-could-mix-diy-concrete-for-cheap-moon-base.html

Back when I was an undergraduate at the South Dakota School of Mines & Technology, concrete was a big deal. The Civil Engineering department students made a canoe out of concrete and raced it in a national championship – winning more than one of the years I was there. We even proposed a project to NASA’s Reduced Gravity Student Flight Opportunities Program (RGSFOP) where students would fly in the Vomet comet KC-135 for the purpose of mixing high strength, fast cure epoxy to determine whether the concrete mixture would have a different chemistry while curing in Zero-G. But it was always clear to me that Concrete was a somewhat ambiguous substance to most people, subject to misunderstanding and generally eschewed.

The first major misconception is the difference between concrete and cement. The terms are generally used synonymously by the public, but there is a major difference. Concrete is loosely defined as a mixture of cement, aggregate, and sometimes, water that are mixed to form a hard, strong building material. The official civil engineering definition (found on CivilEngineeringterms.com, http://www.civilengineeringterms.com/civil-engg-construction-and-graphics/definition-of-concrete-concrete-history-and-strength-concrete-popularity/) is a little too strict, mentioning specific types of cement, including Portland Cement, the most commonly used cement. If that was, in fact, the case, the Concrete Canoe competition would not be possible as the canoes are built from epoxy as the cement and styrofoam pellets as the aggregate. So, by the loose term we could also consider jello with fruit cocktail as a very weak, tasty concrete.

The other major misconception is that concrete is not a sophisticated material. While in its simplest form, concrete was a technology accessible to ancient civilizations – I remember visiting Egypt and all the buildings on the outskirts of Cairo were poured concrete with steel rebar sticking from the roof (the buildings were unfinished for tax purposes). Heck, even I am excited about someday building my own concrete counters into my house – and if I can do it… Modern day concretes are stronger in compression than, I think, any other building material, and creative designs allow for concrete to be used in long spans and towering structures alike. The concrete canoe floats – how is that not sophisticated?

So that being said, is concrete a suitable building material on the moon? Well there are some plusses and some minuses.

The Plusses

Concrete is only really strong in compression. Thanks to modern day building designs, spans can be built by steel reinforcement that brings a long span normally in tension to compression. The significantly reduced gravity of the moon means that concrete can cover much larger open distances with reinforcement than on earth. Since the material gains strength by adding thickness, extra thick walls are also consistent with the need to add particle shielding for any human habitat on or near the surface.

Finally, there is some interesting ideas about how raw materials found on the moon’s surface could be manipulated to make concrete using the loose description we talked about above. In this paper, elemental sulfur could be used as the cement to bind raw aggregate regolith from the moon’s surface to make a kind of concrete. The process is simple, heat up sulfide rich rocks to extract the raw sulfur. Melt the sulfur at it’s low melting point (somewhat above 113 degrees C) and mix it with the aggregate. This mixture of sulfur and moon rock would behave something like asphalt at temperatures that are comfortable to people.

It seems possible that this could be done and at a large cost savings compared to bringing in steel or other prefab modules. If all the materials are present, the only thing an astronaut construction crew needs to do is generate energy (easily done from harvesting solar energy or nuclear reactors) and bring the manufacturing equipment to do this work. Scouting out suitable locations that have the correct dirt is also important, but feasible even today. After some period of time, the cost of building from processed materials onsite can be much less than the cost of shipping in every pound of building materials.

The Minuses

How feasible is bringing the infrastructure to do this kind of work on the Moon? It took twice as long and a hundred times more than anticipated to build the International Space Station. The equipment to create concrete on the moon must be even more sophisticated and reliable than anything we have sent to space to date. At this point, the space industry has expertise in building modules that fit together. I might agree that a new technique would be required to have real outposts on the Moon, but I think that many of the first outposts will focus on the task oriented prefabbed habitats that are similar to the ISS.

How does concrete behave in a vacuum in reduced gravity? This is a question that I do not think has been answered. While I think the paper that this story is based on was well done, I suspect that it was not done in temperatures or the kind of vacuum that exists on the moon. I am certain it was not done under reduced gravity conditions that could have a significant effect on the strength of the material. Even the simplest idea of how do you handle an asphalt-like substance on the moon makes me wonder if it is possible?

I think this is a fantastically interesting topic. If travel to the moon becomes routine within my lifetime, I hope to hear more about building with concrete.  

We must not allow an REE gap! - Part II

This news article is juicy, and it makes me scratch my head - the Molycorp guy is saying counter-intuitive things about the market that will not necessarily improve the company's standing. 

Question: If the industry that utilizes REEs is nearly entirely outside the country (electronics companies are mostly based in eastern asian countries), does it matter if the huge majority of the REE mines are outside the US? Based on this line of reasoning, it seems that the geopolitics between Malaysia or Taiwan and China is more crucial than the US and China.


Update: Ok, re-reading. He does say that China is reducing export quotas and that his company is starting a new mine and expects to produce at a lower cost. The rhetoric banter was slightly hidden by a clumsy reporter and a dislexic reader.

We must not allow an REE gap!

This is a somewhat interesting article about Rare Earth Elements on Geology.com. The part about how crucial rare earths are in common items like rechargeable batteries is not detailed. I think that is a key detail because the trend to use batteries and other rare earth bearing technology is going to increase dramatically in the next decade. 

One story that comes to mind is about Molycorp at Mountain Pass, CA. I spent parts of a few summers across the highway fooling around in the Mojave high desert. Molycorp is one of the few economic rare earth mining companies in the US. They were shut down around the end of the time I was there. 

Everything I heard about why the mine was shut down were rumors mostly from miners that wandered in to camp from the desert. The story was that the operation killed a number of endangered desert tortoises, a serious offense in liberal California. The result was that the mine was raided by federal SWAT and shut down, a bit overkill, even for that state. The conspiracy story I was told for the extreme shut down was because one of the Senators had an investment in a Chinese rare earths operation and that he strongly encouraged the action in order to reduce competition and line his pockets. 

What I know about the story is that at one point I visited while they were in Care and Maintenance mode (basically not producing), they have been actively exploring the region for similar deposits for the past twenty years, and I talked to their mine geologist well after the first closure, suggesting that they had some kind of production.

It is unclear to me if any of the conspiracies have a grain of truth at the juicy center, but if they did, it seems like a pretty damning failure of national security to allow our country to be dependent on a foreign country for the sake of some rich senator's pocketbook.

Deep Underground Science and Engineering Lab - Topography Shielding Part III

The best way to calculate permutations for the endmember cases of muon flux at the DUSEL 8000 ft level campus. 

Best case: Say the entire depth of the lab is a full 8000 feet below the lowest ground surface. Also, assume that the rock is very dense Iron Formation with a specific gravity of 6.0. The calculation is simple, 8000ft of rock * 6.0 g/cc / 1g/cc water / 3.28 ft/m = 14,600 MWE, meters of water equivalent. This is more than double the estimated MWE.

Worst Case: Assume that the 8000 ft campus is actually 7000 feet below the ground surface because of topography. Also assume that mining methods of removed about 75% of the in-place rock and backfilled it with sand. This sand would be largely dewatered by gravity drain effects and have an air void volume of about 30%. Any water that remains trapped in the pores of the rock will increase the effective density, but we ignore that here. Finally, we could assume that the rock would be a granite-like composition with a specific gravity of about 2.85. The in-place rock would be 1,750 ft thick * 2.85 g/cc Qtz / 1 g/cc water / 3.28 ft/m = 1,520 MWE. The sand would have a thickness (7000 ft total depth-1750 ft in-situ depth)*(100%-30% sand volume) = 3675 rock in-place equivalent. The rock-in-place equivalent should have a similar specific gravity so: 3675 ft * 2.85 g/cc Qtz / 1 g/cc / 3.28 ft/m = 3190 MWE. The two values are additive so 3675 + 3190 = 6865 MWE. This is only slightly below the estimated 7000 MWE for the 8000 ft level. 

The best case scenario is more than double the published estimate for the MWE. This estimate is also likely a significant overestimate because the iron formation is not largely extensive around Homestake, it is some fraction of the total thickness of the rock over the 8000 ft level campus. 

The worst case scenario is close to the estimated value, suggesting that the DUSEL folks were being conservative. I can not imagine a case where the ground below Lead would not be actively caving in with a lower MWE (although it is subsiding). In the muon flux shielding world, more is always better, so I can confidently conclude that the the MWE shielding estimate is a good one and likely to prove more effective when the lower campus is built.

Deep Underground Science and Engineering Lab - Topography Shielding Part II

Meters of water equivalent, m.w.e. is the unit of shielding used to describe how much muon flux can be filtered by placing an underground lab at a certain depth. I did a calculation looking at the mwe reported for the DUSEL. DUSEL's main cavern will be placed at approximately 8,000 feet below ground surface and the mwe is reported as 7,200. With a little unit conversion mathemagic, the specific gravity that the scientists used was 2.95. The density of water is 1 gram per cubic centimeter and specific gravity is the factor of times more dense than water. So, the scientists that estimated the mwe for Homestake used some kind of logic that assumed the rock above the lab was 2.95 times the density of water. 

This is interesting for a few reasons. 1) The 2.95 is close to the average density of continental material, the kind of thing that a physicist would look up in a book. 2) The Homestake formation and the surrounding units are highly metamorphosed greenschists, quartzites, and iron formations. The specific gravity of these units, in place, is about 2.85 on the low end for relatively light quartzite up to 5 or 6 for heavy iron formation. The estimate for specific gravity may be low by a bit under a factor of 2. 3) The 8,000 foot depth is based on a mine coordinate system that has a zero elevation somewhere near the top of the open pit (the zero point was mined out when the Homestake company opened up the pit in the 1980s). Anyone who has been to Lead knows that those hills are as much as thousand feet high. The actual depth from the collar of the shaft is much different than the depth from the Kirk trailhead to the 8000 foot level. And 4) the mining method was vertical stope retreat where large blocks of material were mined away and then refilled with a sand slurry. This fill material could be a relatively large fraction of the material between the lab and the ground surface. All of these factors are sure to introduce uncertainty in the back of the envelope mwe calculation. 

Instead, I would suggest using the block model that Barrick trusted to the state to estimate mwe. The computer model includes all the geologic formations, known rock density from drill core, and accurate 3d locations of the drifts and ground surface. These parameters could be used to estimate the mwe for any location that was sampled with diamond drill holes or mined during Homestake's operational period. The alternative would be to characterize the muon flux by accessing the opened caverns and directly measuring the flux. A final option would be to measure the gravity at each level and use the results to determine the effective density of the ground between levels - this method would provide a better understanding of the backfill and dewatering which could change the density after geologic modelling was completed by Homestake. 

I think tomorrow I want to look at the permutations of the best and worst case scenario for specific gravity of the ground above the DUSEL caverns.

Deep Underground Science and Engineering Lab - Topography Shielding

There is a figure that the Deep Underground Science and Engineering Lab (DUSEL) guys were bandying about back when the NSF was making its initial decision on which underground facility would best suit an underground neutrino detection lab, maybe seven years ago. The figure showed Homestake mine was the deepest candidate with operational facilities at 8,000 feet below the ground surface. This was considered favorable because the deeper the lab was buried the more cosmic rays would be filtered out. This was good because those pesky cosmic rays interfered with the neutrino detectors (the neutrinos were not affected by the earth above). 

My question is how the topography of the ground and the density of the ground change the shielding properties of the earth above the neutrino lab? I know this work has been done already to some extent. I had a conversation with Bill Roggenthen who told me Wick Haxton at U. of Cal Berkely did the theoretical work and Nicolai Tolich at U of Washington looked at the topography issue. But I still don't think anyone has looked in detail at the properties of the rock surrounding the lab, which could impart a directional shielding effect. 

Talking to my friend Mark, who is helping with a little experiment called LUX at the DUSEL, he says the important thing to look for is how many Muons can be shielded with depth. I told him this would be a problem since I did not believe in Muons, but he insists they really exist. So, if anyone is interested, I want to look into the question and you are welcome to join me. It is work that is likely already done or could be tested in a few years when the lower levels of the lab are developed and the muon background is directly measured. But it is a fantastic question and probably will impart lots of edumacation in the process.

Chilean Miners Saved - A technical marvel!

How did they drill the hole that allowed the Chilean miners to escape? 

There are a couple different methods I can think of. The fundamental problem with drilling a deep hole down is how do you remove the chips of rock ground ahead of the bit from the hole? Usually drillers use some kind of media like water, heavy drilling mud or even high pressure air to float or blow the chips out. 

If there is a column of mud or water a few thousand feet high, the pressure on the escape cavern (which housed the miners) is tremendously high and could either flood the cavern with liquid or overpressure the tunnel if it broke through. My guess is that they calculated how far they could drill on water and then pumped the hole down and then dry drilled the remaining segment. This would be inefficient drilling but might be the easiest way to not kill the surviving miners. 

I'm also thinking that they drilled numerous holes to feed water and food to the guys trapped for 69 days. Smaller diameter holes are easier and faster to drill and I imagine they could have burned through bits and blew out chips in the rush to get that first hole sunk. I remember at the beginning they could only send a small video camera to communicate with the miners by recording messages. This suggests to me that the first hole was only a few inches in diameter.

I have not been following the news in detail and the story might be out there. It would be slick to get the story linked or get some expertise from my geo friends who have spent more time on a drill rig.

This is an amazing recovery story and I'm happy for the survivors. Props to the brave medics who went down first and presumably came up last.