Native arsenic. 
This sample of native (naturally occurring) arsenic is from the Burraton Coombe Quarry, St. Stephen-by-Saltash, Cornwall, in the UK. 
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 
Price: Donated 
Size: 1" 
Purity: >80%
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