It's interesting that the subject of minerals has been brought up on the list, and I'll take advantage of the slightly off-topic thread to ask a question of the fossil hounds out there.  Has anyone seen or collected old crystallized coral?  I think the crystals are called calcite, but I'm not too familiar with this field.  I've been finding old coral pieces that have "yellowed" and started forming crystal points, and I was wondering if this is a common find in the fossil shell pits.
Thanks for your help,
Joni