Sprial Shell-Geode-Fossil?

[kgraeff]

We are in Tampa, Florida. The rock this was originally found in was one among many being used for erosion control, so I am unsure of its origin. It caught my attention because of sparkling geode sections that were exposed. When we attempted to crack it open, we came across several seashells which have been become geodes. I am having a difficult time finding information on this online, and perhaps I am just putting the wrong information into Google? If you all could help I would greatly appreciate it!

[Harry Pristis]

Here's one likely source of your rip-rap:

http://www.thefossilforum.com/index.php?/gallery/image/15106-florida-crystals/