Hope you guys can help me. I found this mineral shell about 25 years ago in the Philippines. It not a shell but what was inside the shell it became some sort of marble mineral. As if the shell's purpose was just to be the cast of this mineral. Still new to this site so I'm not sure how to post photos.
"Internal casts" of gastropod shells, and even bivalve shells, are a common type of fossil. It sounds like that is what you are describing. Â The empty shell gets filled with sediment which eventually becomes bound together into a solid mass, while the actual shell, being made of much softer calcium carbonate, slowly dissolves away leaving the internal cast.
Some information on posting images can be found here:
<a href="http://www.seashell-collector.com/Html/acebordHELP.htm" target="_blank"><!-- m --><a class="postlink" href="http://www.seashell-collector.com/Html/acebordHELP.htm">http://www.seashell-collector.com/Html/acebordHELP.htm</a><!-- m --></a>
Even if you don't have your own homepaqe or website, many servers provide a certain amount of free webspace where you can post things. Otherwise you can try one of the free posting sites. If you are unsuccessful, email the image to me and I will post it for you.
Regards,
Paul  <span class="petit">--Last edited by Paul Monfils on 2008-05-24 22:55:37 --</span>
Hopefully this works
<a href="http://www.badongo.com/pic/3638941" target="_blank"><!-- m --><a class="postlink" href="http://www.badongo.com/pic/3638941">http://www.badongo.com/pic/3638941</a><!-- m --></a>
Fossils are not my specialty, but this does not look to me like an internal cast. It looks like a complete shell, probably agatized. Â If we don't get any more information here, I'll ask the folks on Conch-L to take a look. There are a few good fossil folks there.
Thanks for your feedback Paul!