Chromium Petrified Wood.  
The tag that came with sample reads as follows:Jurassic, Arizona USA 
This wood has been minerally replaced with Chromium giving it a green color.  Very little of this wood has ever been found, making it very rare.  This wood is a natural hygrometer, when dry it becomes a very light pale green and when wet or exposed to humidity it turns a deep green.  
Source: Fossil Image Ltd. 
Contributor: Theodore Gray 
Acquired: 29 March, 2003 
Price: $15 
Size: 2" 
Composition: Cr
 |  
  |  
 |  
  |