|Depleted uranium cylinder.|
After several false starts, I now have an indisputably genuine, solid machined cylinder of pure depleted uranium metal. Although vast quantities of this stuff exist (vast as in at least a million tons worldwide), it is incredibly hard to get a hold of. This is because there are no uses for it that are not fairly tightly regulated: Most are military, and the civilian uses are for things like aircraft counterweights or radio pharmaceutical shipping containers. Not the sort of thing that's likely to end up in the local surplus auction.
The "depleted" in "depleted uranium" refers to the fact that the percentage of highly radioactive U-235 in it has been reduced from its naturally occurring concentration, leaving a larger fraction of the less-radioactive U-238 that makes up the vast bulk of natural uranium. But depleted doesn't mean eliminated: In fact the radioactivity of depleted uranium is only about 20% less than that of naturally occurring uranium!
That means this cylinder, though depleted, is still the most radioactive thing I have in my collection. It represent about 140 microCuries of total activity (about 300,000,000 disintegrations per minute). A Geiger counter held up to the side of it will read about 100,000 counts per minute. Fortunately, the radiation from uranium and its decay products is mostly in the form of alpha particles that do not penetrate skin. Holding this cylinder is probably not particularly harmful, though it's not something I do for any longer than necessary to shock people. (There is almost certainly a greater health hazard associated with any uranium oxide that might form on the surface and get onto hands and into lungs from there. For that reason I have put a thick coating of varnish over the cylinder. The main sample photograph was taken before I varnished the cylinder, while the 3D version was made after, and clearly shows the thick, glossy varnish.)
I acquired this cylinder legally, by trading the rare historical Revigator booklet described above to a prolific collector of radioactive stuff. He wishes to remain anonymous, because he does not want to become known as a person with uranium to hand out. To the best of my knowledge there is no source anywhere in the world from which it is possible for an individual to buy solid machined uranium metal in small quantities at any price. (And large quantities require special licenses to handle.) But see above for a lot of different things you can buy that contain some amount of uranium. It's also very easy to buy uranium ore from any number of mineral shops or on eBay.
Acquired: 21 December, 2002