Off-topic: what will happen to my tungsten cube?
February 26, 2018
In her best-selling book, The Life-Changing Magic of Tidying Up, Marie Kondo argues that you should get rid of everything in your life that doesn’t “spark joy”. I have accepted that I will never achieve Kondo-level simplicity, because too many things spark joy: a brass dinosaur my grandmother gave me when I was a kid, a worn penguin tibia I picked up on a beach in Uruguay, an Oklahoma rose rock, the alligator head Vicki brought me from New Orleans, an armadillo skull I found in the woods once, a sliced geode, an ammonite…the list goes on. Every area I have control over becomes, if not a cabinet of curiosities, at least a semi-organized array of curiosities.
An old box of stuff I unwrapped over the holidays. The human skull and allosaur claw are casts, all the other natural history items are real.
There are a couple of objects in my collection that give me more pleasure than any of the rest. One is a piece of shrapnel from the Sikhote-Alin meteorite – more about that another time, perhaps (done). The other is a 1.5″ tungsten cube.
I got the tungsten cube because of an answer on Quora to the question, “What is the most beautifully satisfying physics-based desk toy?” As the anonymous author of this particular answer wrote:
Some philistines may not consider this a proper “toy”, but I’ve had one for a year or so and am still crazy about it and have zero regret about purchasing it despite its high cost. It doesn’t do anything other than be way heavier than it seems possible for something that size to be. I think it’s mind-boggling and entertaining just to pick it up, hold it, savor its surreally strong attraction to the center of the earth, and think about gravity, matter, fundamental forces, etc.
The next time I got a nice chunk of fun money, I got the pair of 1.5″ tungsten and aluminum cubes sold by Midwest Tungsten Service. And a couple of years on, I gotta say, that purchase has probably given the best return of enjoyment per dollar of anything I’ve ever bought. For two reasons.
First, there’s the tactile enjoyment of picking up the tungsten cube. It is shockingly heavy. Pure tungsten has a specific gravity of 19.25. This cube is an alloy of 95% tungsten, 3.5% nickel, and 1.5% iron, called MT-18F by Midwest Tungsten. According to the fact sheet provided with the cube, “The addition of these alloying elements improves both the ductility and machinability of these alloys over non-alloyed tungsten, which can be brittle.” The addition of those other elements brings the cube’s density down to 18 g/cm^3. By comparison, steel is 8.05 and lead is 11.35. So even the alloyed cube still has a density more than half again that of lead. The 1.5″ cube has a mass of almost exactly 1 kg.
Even knowing, intellectually, how heavy the tungsten cube is, it’s still a kick in the brainpan every time I pick it up. It feels unreasonably, unnaturally heavy. It’s uncanny, like something out of a comic book, like it’s being pulled downward with the same force I normally associate with strong magnets.
The second reason why the cube is so great is the thoughts that it inspires. Pure tungsten has a melting point of 3422 °C (6192 °F). The W-Ni-Fe alloy, like other tungsten heavy alloys, “will begin to form a liquid phase when heated in excess of ~1450 °C (2642 °F)”, according to the Tungsten Heavy Alloy Design Manual (link). According to this page, most room fires max out at about 1200 °C, and according to this page, the temperatures of most magmas are 700-1300 °C (~1300-2400 °F). W-Ni-Fe alloy is also extremely hard, with a Vickers hardness of 262 kgf/mm² (about 8.5 Mohs; regular steel is 4-4.5 and hardened steel is 7.5-8). The only harder substances are things like corundum; carbides of silicon, titanium, and tungsten; boron; and diamond.
So, seriously, what is going to destroy this cube? Burn down the house, and it will survive. Toss it into lava or magma, and it will sink to the bottom – even into the upper mantle – and sit comfortably, 150°C or more below its melting point. If I owned beachfront property it would be cool to put the cube on a pebbly part of the beach and leave it there for a few years and see how – or if – it would erode. I know it can shatter if hit hard enough, but I imagine if it was just rolling around in the surf with some pebbles, the tungsten cube would wear down the pebbles and not vice versa. (It occurs to me that this could be tested with a small cube and a rock tumbler – I’ll let you know if I ever perform that experiment.)
My youngest brother, Ryan, designs drill bits for the oil industry, and then goes out to the drill sites to see how they wear down. His job is basically getting industrial diamond, tungsten carbide, and hardened steel to play well together at 1100 rpm. I wrote to get his profession opinion on the survivability of the tungsten cube.
Me:
I’m having a hard time thinking of some natural or accidental process that would destroy it. Volcano, asteroid, and A-bomb are all I’ve come up with. [This was before I’d looked up the temperature of magma.] Like, if it just got left out in the rain and the sun forever, would it corrode? Ever? How long could it be sitting there as a recognizable cube – a century, a millennium, 100,000 years?
Ryan (in an email with permission to cite):
I don’t have much experience with straight tungsten but WC [tungsten carbide] should fare better corrosion wise, it takes some pretty exotic stuff to corrode it. Now cobalt has a melting point of 2700F so if the WC got that hot the cobalt binder would melt, desintering the WC and breaking it down. However that’s way hotter than your average house fire.
Barring any natural disasters, acts of God, or man-made intervention, I would think you could set that thing on the ground somewhere and it would be just fine for a long, long time.
Fun fact #1: Pure tungsten oxidizes in air, so I imagine that’s one of the reasons they added the nickel in the MT-18F.
Fun fact #2: Ni and Co have very similar melting points. [Meaning that my W-Ni-Fe cube will desinter at about the same temp as tungsten carbide, which uses cobalt instead of nickel as the binder.]
My desk at work. Aquilops and sea otter skulls on the left are casts, the ichthyosaur is a 3D print, and everything else is real and mostly collected and prepped by me. That’s the aluminum cube in the back on the far left. The tungsten cube sits on my side of the desk, where I can play with it.
Now, I have a lot of things that I hope will outlive me, including a lot of old books and reprints. And a lot of that stuff is pretty durable, including the aforementioned meteorite chunk. But there is a big difference between holding a century-old monograph and hoping that the people who come after me will care for it, and holding the tungsten cube and knowing that it will most certainly survive for centuries or millennia, unless someone attempts to destroy it, deliberately and with a non-trivial expenditure of effort.
And that’s why I’m writing about the tungsten cube here on what is normally my fossil blog. I am surrounded by objects that represent time – developmental time for bones, geologic time for fossils and minerals, astronomical time for meteorites – but these are almost all natural products that embody the past. The tungsten cube is a human product, and in its sheer durability – and survivability – it embodies the future. It will exist in future iterations of this world that I can’t imagine. That’s a breathtaking thought.
If you’re thinking about getting a chunk of tungsten, I strongly recommend the 1.5″ cube set. A few months after picking it up, I got a 0.5″ cube of the same stuff, just to see what it would be like. It’s heavy for its size, but it’s not heavy enough to be shocking. The visceral reaction is more “huh” than “WOW!!”
It’s worth getting the set because the aluminum cube is also entertaining and it’s worth the small additional outlay (as of this writing, $133 for the 1.5″ tungsten cube alone, and $159 for the pair). The aluminum cube has a mass of 0.15 kg, exactly 15% that of the tungsten cube. I have visitors pick up the aluminum cube first. It’s funny, I guess a lot of folks haven’t had a chance to play with solid chunks of metal firsthand because they’ll pick up the aluminum cube and say, “Wow, that’s heavier than I expected.” At that point I just smile. The tungsten cube blows people away, every time. Heck, it blows me away every time, and I’ve been playing with it for two years. Highly recommended.
For a full line of cubes, spheres, and tops, check out Midwest Tungsten Service (link). Many of their products are also available on Amazon.
Sauropod Vertebra Picture of the Week 
February 26, 2018 at 11:53 am
If I owned beachfront property it would be cool to put the cube on a pebbly part of the beach and leave it there for a few years and see how – or if – it would erode.
Surely you’d lose it: it’d sink.
Maybe you should just gather a big jar full of pebbles, sit the tungsten cube on top of it, and see what happens then.
February 26, 2018 at 4:23 pm
Surely you’d lose it: it’d sink.
Yeah. Even in the tidal zone, it would surely work its way down among the beach stones. Most of Earth’s surface rocks have densities less than 3.5 g/cc and even fairly heavy stuff like hematite is only about 5.5 g/cc. So at 18 g/cc the tungsten alloy cube is roughly six times as dense as the rocks it would be rolling around with. I think it would be like setting a steel ball bearing in a tub of popcorn and then shaking the tub.
Maybe you should just gather a big jar full of pebbles, sit the tungsten cube on top of it, and see what happens then.
You mean with the cube inside the jar, atop the pebbles, and let the jar roll around in the surf? That’s the only way I can see doing it and not having the cube just get lost. But there’d still be the risk of the jar getting lost or destroyed. I mean, what do you use for the jar? Not glass, obviously. Most metals will either be subject to some level of corrosion, or will be hard enough to beat up the pebbles some themselves, or both. Rubber and plastic will probably both degenerate too fast if they’re constantly exposed to the sun and the waves. Maybe a sort of carbon fiber beach ball.
But at that point, I think you would have just recreated a rock tumbler at considerable expense and under less controlled circumstances. So might as well just go to a rock tumbler in the first place. Turns out there is an extensive and pretty sophisticated literature, going back decades now, on using rock tumblers to simulate erosion and weathering processes (thank you, Google Scholar and Sci-Hub). So if I ever do get around to doing that experiment, I’ll at least have some guidance.
February 26, 2018 at 7:45 pm
my W-Ni-Fe cube will desinter at about the same temp as tungsten carbide, which uses cobalt instead of nickel as the binder
You said your cube was alloyed with nickel, not sintered with it as a binder, so it won’t de-sinter. It should start to soften at the eutectic point of the tungsten-nickel-iron system
The internet tells me the tungsten-nickel system has a eutectic at 1,495°C, so I can well believe adding iron would lower that to 1,450°C. But ternary phase diagrams are fearsomely hard to represent visually, and I saw no such diagram, only the binary one.
February 26, 2018 at 7:50 pm
No, I just meant let it sit. I mean, I guess you’d need some kind of movement to make any thing happen. Maybe keep it in your jacket pocket for a day, as you move around?
February 26, 2018 at 8:29 pm
derek, as far as I’ve been able to tell, when most sources talk about heavy tungsten “alloys” what they really mean is tungsten powder sintered together with various binders, not melted and mixed like you’d expect with, say, steel. So possibly I am being imprecise by referring to the sintered heavy tungsten “alloys” as such – but if I’m wrong to do so, apparently so is the entire industry. In any case, the heavy tungsten alloys produced by Midwest Tungsten Service are made by sintering tungsten powder – MTS describes this on their webpage and in fact sheets – so presumably they will desinter if they get hot enough.
Mike wrote: No, I just meant let it sit. I mean, I guess you’d need some kind of movement to make any thing happen. Maybe keep it in your jacket pocket for a day, as you move around?
I’m sorry, I am not grasping your point. What would you expect to happen if the tungsten cube just sat on a pile of pebbles? Wouldn’t it just…keep sitting there? And if the pile is agitated, like a jar of bits rolling around in my pocket, isn’t that just a very low-grade rock tumbler?
February 26, 2018 at 8:42 pm
Oh. Maybe you mean put the tungsten cube in a big jar of pebbles and leave that open-topped outdoors, to see if sun and rain would have any effect? I have considered doing something like that. I doubt that any change would be visible within my lifetime, but I guess that alone would make it worth doing, especially since little cubes (1-1.25 cm) can be had for $20-30. But I’d like to do the rock tumbler experiment, too, to simulate what I think would probably be worst-case conditions of a cobble-bottomed river or a rocky beach.
I’m tempted to get a spare chunk of industrial tungsten or tungsten carbide, something ugly that would be unlikely to walk off, and toss it in the flower garden. In particular, it would be interesting to see how fast a chunk of tungsten would work its way into the ground just from collapsing the soil spaces beneath it, like earthworm tunnels.
February 27, 2018 at 7:52 pm
This does sound fascinating. For any billionaires reading this, cubes of osmium are also now available, weighing in at a crushing 22.6 g/mL, with menacingly sharp corners. The 25 mm cube is a steal at $20,000:
http://luciteria.com/metal-cubes/osmium-metal-cube-999
February 27, 2018 at 11:09 pm
And if the pile is agitated, like a jar of bits rolling around in my pocket, isn’t that just a very low-grade rock tumbler?
Exactly. A low-grade rock-tumbler that you already own.
February 28, 2018 at 12:30 am
Ha, yeah. But decent rock tumblers are cheap. You can get a rubber-lined one with good reviews for like $70, and it’s something London and I have been talking about doing for other reasons anyway.
One nice thing you can do with a rock tumbler is estimate how far a sample would survive tumbling downriver in a cobble-bottomed channel. From Coffey and Mattox (2006: p. 37):
Each rock falls about 15 cm (the diameter of our tumbler) with each revolution. We can quickly estimate the distance each cobble travels per day:
15 cm × 20 revolutions × 60 minutes × 24 hours
= 432,000 cm
This is equal to about 4,320 m or 4.3 km (2.7 miles) per day. Going back to the data collected, we can estimate how far a rock travels before it would be abraded to silt or mud-sized particles. For example, the slate survived about four days. Each day it traveled about 4 km. So, by the time it had been transported only 16 kilometers from its source, it had been worn down to mud-sized particles. Weathering and erosion would reduce the limestone cobble to fine particles after about 30 days of transport.
They then go on to estimate how long a sample would survive if the current necessary to move it (>5 m/s for most cobbles) only comes along once a year, once a decade, etc.
My prediction, without having done the experiment yet, is that a tungsten cube among similar-sized cobbles of surface rock would survive as a recognizable object for a transport distance longer than any river on Earth. But really that’s unrealistic: the tungsten is so dense that instead of migrating downstream it would surely work its way down into the very first depositional opportunity it encountered, like a lag or bar.
That in turns brings up the interesting question of how long a tungsten cube would survive as a recognizable clast if it were buried and incorporated into a lithified sedimentary conglomerate. I feel another email to Ryan coming on.
Reference
Coffey, P. and Mattox, S., 2006. Take a Tumble: Weathering and Erosion Using a Rock Tumbler. Science Scope, 29(6), pp.33-37.
February 28, 2018 at 12:37 am
Thomas – are you trying to bankrupt me here? I am a total victim for science junk (ask Mike) and I did not need to know about that site!
February 28, 2018 at 8:52 am
I feel a sci-fi story coming on, where the premise is that deep in a mine, someone finds a tungsten cube from the Mesozoic.
February 28, 2018 at 8:42 pm
That’s more or less what started this whole line of inquiry: it seems plausible that humankind’s durable tools will be the most geologically persistent evidence of the Anthropocene.
March 1, 2018 at 3:01 am
This was a wonderful post.
March 3, 2018 at 5:49 am
how about having it engraved with some sort of deep time message and leaving it in a remote place?
March 3, 2018 at 7:38 am
Interesting idea. A sort of Voyager record to the future. I wonder what kind of inscription would be detailed enough to contain the seeds of its own deciphering, but still coarse enough to survive the passage of eons. I guess it depends on what we want to say to the future. If all we need is a “we were here”, it might be hard to improve on a stark geometric solid with an internal structure consistent with no natural process – the time capsule equivalent of brutalist architecture.
March 3, 2018 at 9:22 pm
The platinum metal cubes are a bit much, especially the Rhodium one but the Rhenium cube is potentially buyable and even heavier than the Tungsten one.
Some of those metal cubes may well be around for a very long time indeed.
You could imagine some future archaeologist trying to discern the meaning of the element symbol on them.
Another thing that may last surprisingly long is bronze statuary; there are a lot of old examples in archaeological collections.
March 3, 2018 at 10:55 pm
And the other man made objects that may last a very long time may be artificial gemstones like cubic zirconia, moissanite, yag and cubic boron nitride; and also lab grown corundum crystals.
Based on the time diamonds and other gemstones last you might expect them to last on a geological timescale.
March 4, 2018 at 10:03 pm
Don’t let your grandmother read this. She’d be as disappointed as I was her heartfelt gift didn’t make it to a photo! Imagine what she was thinling as she was buying it for you! :-(
Funnily enough I was just talking to myself about tungsten today. That wolframalpha.com bloke writes kind of heavy and hard (and he goes on forever), and it seems right he should hold the real name of tungsten.
I too have an alligator head, but checking it yesterday by chance, I noticed quite a lot of insects seem to have pupated in its mouth. You might want to watch out for that. (Mine was properly taxidermied, of course – not raw or anything.)
March 5, 2018 at 3:14 pm
What’s that, Frodo? You’ll take it?
March 5, 2018 at 3:26 pm
:-D
It was made in the fires of an industrial kiln. Only there can it be unmade.
March 5, 2018 at 7:37 pm
See also: Where the Council of Elrond went wrong.
March 5, 2018 at 11:09 pm
LeeB – there’d be a lot more bronze (and gold and silver) artifacts if they weren’t so easily turned into new stuff with a little heat. Most ancient bronzes survived because they were hidden underground or underwater; any left out where they could be gotten at, were.
March 9, 2018 at 5:56 pm
I now desperately want a tungsten cube.
March 9, 2018 at 8:28 pm
A gold cube would work too (well, if one could afford it in a toy)… people don’t handle enough gold to realize it’s so heavy, a bit heavier than tungsten in fact. I was a forensic scientist many years ago and Tungsten was the material of choice with criminals for faking gold ingots – except that because it’s so brittle, they’d embed tungsten rods in a thin cover of lead, then gold plate the lot.
March 9, 2018 at 8:45 pm
Very cool, Nathan. While reading around about tungsten, I’d heard of people using it as a substitute for gold in ingots, but I never had any contact with anyone who had experienced this in the real world. Not that I doubted it! But thanks for the report.
March 10, 2018 at 7:51 am
You’re welcome, Matt. I myself never had much contact with anyone who was into sauropod vertebrae (or into theropod vertebrae, for that matter) but I I’ve been enjoying your blog for years…
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