This sample of metallic cerium arrived coated in mineral oil in a plastic bag, because it would otherwise likely have oxidized away in transit. I cleaned it up some and put it in a dish covered with fresh mineral oil.
It happened to arrive in my mailbox on the very day Oliver Sacks was visiting the Periodic Table Table, so we got to open it together.
Source: Andrew Goodall
Contributor: Andrew Goodall
Acquired: 12 November, 2002