Native Arsenic with Loellingite.  
This heavy (and toxic!) lump of naturally occurring arsenic contains a small, light colored inclusion of loellingite, which is FeAs2. 
Source: Frank Liebscher 
Contributor: Frank Liebscher 
Acquired: 28 January, 2004 
Price: Donated 
Size: 1.25" 
Composition: As+FeAs2
 |  
  |  
 |  
  |