[Rockhounds] Coprolites

[Pmodreski at aol.com]

In a message dated 4/8/2008 9:56:11 PM Mountain Daylight Time,  
nospam at orerockon.com writes:

The  fresh, un-eroded concretions are iron oxide, the eroded 
concretions have  been oxidized in the air and in the stream to iron 
siderite. The  explanation is quite simple. Get some concretions from 
the un-eroded clay  in the Wilkes, and from the stream bed. Analyze 
both. Then you will see  that the "poopy" iron siderite nodules are 
simply eroded forms of the iron  oxide nodules.



No, sorry, that can't be it.  Siderite (ferrous iron carbonate, FeCO3)  
oxidizes to limonite, not the other way around.
 
Pete
 
(never been to the locality, but I'm pretty sure that a specimen or two  that 
I've purchased over the years, must be from  there)



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