Agatized coral heads are often found in Florida and Georgia, in ancient ocean beds where silica rich groundwater has percolated through the coral heads, and over time has replaced its calcium carbonate skeleton with a hard variety of Chalcedony. This leaves the ornamental fossil with a sometimes banded stone look.
Archaeopteryx Berlin specimen is considered the most famous fossil in the world. It is about 150 Ma & was discovered in limestone deposits in Eichstaett, Bavaria. Archaeopteryx has bird flight feathers, but also has reptile features such as a tail bone &