Vapor grown crystals. 
These small crystals came with a helpful little card, which states as follows: "These crystals are produced in a high vacuum chamber.   The chamber is heated to the point where the metal vaporizes and sublimates onto a glass substrate." 
Source: SoCal (Nevada), Inc 
Contributor: Ed Pegg Jr 
Acquired: 5 August, 2002 
Price: $10 
Size: 0.1" 
Purity: >99%
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