|Heavy 290g lump.|
This lump has one of the most interested surfaces I've seen. Smooth, silky, yet crystalline. It's very heavy (heavier than lead, though not in the same league as tungsten). Words don't do justice to this very interesting hunk of metal. Gillian Pearce, the source, reports that this surface is very characteristic of hafnium, and forms spontaneously any time hafnium metal is cooled from a molten state. I'd sure like to see that happening some day, but the extremely high melting point means it's not something I can do at home.
The rotatable 3D image is particularly good for this sample: Worth the download time. You'll see that the back face is completely different than the front face you see in the main picture.
Analysis by x-ray fluorescence spectroscopy at the Center for Microanalysis of Materials, University of Illinois (partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439) indicates it is 99.25% hafnium, 0.75% zirconium. Hafnium and zirconium are quite difficult to separate, and even very pure zirconium is often sold with the understanding that there is several percent of hafnium contamination, and vice versa. Since they are chemically very similar (which is why they are hard to separate) this is often not a big deal, other than in nuclear applications.
I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.
Source: eBay seller rubbleshop
Contributor: Theodore Gray
Acquired: 19 October, 2002
Text Updated: 4 May, 2007