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3DSurplus 11 pound metal cylinder.
Purchased from Neil Lipson ( after contact through eBay. Said to originate from a company closure.
This is by far the most tactile sample in the collection: People just can't put it down, because it's so darn heavy. I always point out that it's almost exactly the same density as gold, so holding this lump is as close as you're likely to come to the experience of holding about $50,000 (at $350/troy ounce) worth of gold.
I had a suspicion that it was probably not pure tungsten. Research on the internet indicated it was probably about 97% tungsten, 1% iron and 2% nickel. The iron and nickel are mixed with tungsten powder and the mixture heated under great pressure to fuse the iron-nickel alloy into a matrix around the tungsten particles.
Through the good graces of Inga Karliner of the University of Illinois physics department I was put in contact with Ivan Petrov of the U of I's materials research department, which just happens to be a national collaborative center for materials testing, which means they have a hallway with something like two dozen very fancy instruments for telling me what my tungsten cylinder is made of. (I was pleased that even at a national collaborative center for materials testing my tungsten cylinder was considered interesting and heavy.)
Petrov's colleague Jim Mabon confirmed my guess with a quantitative analysis by x-ray fluorescence spectroscopy;
96.32% tungsten
1.23% Iron
2.45% Nickel
(Per the terms of their service, I should mention that this analysis was carried out in the Center for Microanalysis of Materials, University of Illinois, which is partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439.)
Source: Neil Lipson
Contributor: Theodore Gray
Acquired: 29 May, 2002
Price: $315
Size: 3"
Purity: 96.3%