This free model comes with MeshLab, the open-source stl viewer and editor. I cleaned it up a bunch in Blender, then exported to stl and sliced it up with SkeinFox/Skeinforge. Gcode included below (high-res for printing all the fine details -- 0.25 mm/layer).
I've included the source Blender files and also the Blender render environment I used to make the marble pic.
The original model was scanned by the ISTI-CNR and was released under the CC-SA license.