[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Green fossils?



In a message dated 96-10-03 17:23:15 EDT, Sherry Michael wrote:

> Recently, a Morrison specimen we are working on in our lab has begun to
>  turn this wonderful shade of lime green! Both the exposed bone and the the
>  matrix are green. It seems to be some kind of oxidiation compared to
>  fungus, but the color is pretty odd. The bone does not seem to show any
>  signs of breakdown.

Hi Sherry,

It 'sounds' like your specimen has "pyrite rot". It superficially resembles a
fungal or bacterial infection by spreading (giving one the impression of a
biological cause) all over a fossil. My Arundel Clay dino and other specimens
occasionally produce this disease. IT MUST BE STOPPED OR IT WILL DESTROY YOUR
FOSSIL!
 It seems that subaerial exposure  (and water) while in the presence of Iron
and Sulfur  fuel this interesting chemical reaction but attempts to "cure" it
have had mixed results. And as far as the Arundel clay is concerned, it is
LOADED with siderite, biogenically produced sulfur from the acidiic
conditions of the deposit, and lignite. Pyrite crystals and it's weathering
product marcasite, are fairly common. 
As for the cure, I forget the various treatments but in my case, I have been
using an aggressive approach whereby I grind off the pyrite rotted areas
(carefully of course) then I apply  a 50-50 solution of hardener followed by
a spray coating (several actually) of either polyeurethane or epoxy. It is a
very time consuming process and I have been working on one particular piece
of long bone for about two years. Even after this treatment, some pyrite
comes back and I repeat the process. I HAVE noticed a decrease in  the extent
of 'reinfection' as well as ian increase in the time between reinfection
which leads me to believe that I am on the right track. 

But there are simpler alternate methods that I am sure the list members will
be forthcoming with.

Regards,
Thomas R. Lipka
Paleontological/Geological Studies