A needle is vibrated with a jet of air to break loose small rock fragments. The final preparation step is to air abrade the surface carefully with miniature sandblasters. Because baking soda is soft, it is used as the grit to remove the last, thin layers of dirt. The fossil bone is then penetrated with thin glue once more, labeled, and catalogued into the Museum s collection. It is now ready for casting and study.
Fossil bone is the original bone that the animal made.
The bone is not its original white color because of foreign minerals. These minerals were deposited in the bone s pore spaces after the skeleton was buried by stream action. The minerals come from surrounding groundwater and are usually deposited as a result of bacterial action. This fossilization process is called permineralization. In the case of our dinosaurs, iron minerals are mainly responsible for the dark brown color.