When polishing natural diamond anvils, we are sometimes confronted with minor naturals or naives around the girdle of the diamond anvil during the finish polishing step. In order to clean the natural surfaces from any such defects, we must polish a small extra facet on these naturals or naives. This additional facet can be at most up to 1/3 of the pavilion or crown facet size. Furthermore, this facet does not weaken the diamond anvil.
You can find some example pictures here.
Figure 1: Natural/Naive still rough.
Figure 2: Natural/Naive polished as extra facet .