Fig 20. Three-dimensional visualization of the surfaces before and after experimentation.

Process 1 (gravels used on animal skin) has erased the reliefs in favor of hollows and valleys and the polish is more homogeneous. (A) Shows the 3D surface of the experimental gravel before the experiment and (B) shows the surface of the same gravel after the experiment. The picture to the right is taken with petrographic microscope and shows the surface after the process. Process 2 (gravels used on ochred and greased animal skin) has smoothed the surface leaving some hollows and valleys (in blue). (C) Shows the 3D surface of the experimental gravel before the experiment and (D) shows the surface of the same gravel after the experiment. The picture to the right is taken with petrographic microscope and shows the surface after the process. Process 3 (gravels polished with silts from Landry) is the only one to produce striations. (E) Shows the 3D surface of the experimental gravel before the experiment and (F) shows the surface of the same gravel after the experiment. The picture to the right is taken with a metallographic microscope Leica DM2500 M. All treatments produced a strong downward shift on the Z scale.