Diamond powder. 
Looks kind of like graphite powder, doesn't it?  This is very fine (0-1/4 micron) diamond powder intended to be used as an abrasive, and it really looks nothing like a bunch of tiny diamonds. 
Source: eBay seller reginaldvance 
Contributor: Theodore Gray 
Acquired: 1 September, 2003 
Price: $50 
Size: 1" 
Purity: >99% 
Sample Group: Powders
 |  
  |  
 |  
  |