I thought I had mine done already.  I even had thin parallel flakes covering the entire piece.  While taking one of the very last finishing flakes, a crack full of gunk was revealed, about an inch down from the tip, and by the time it was cleaned up, there wasn't much left.  
I wish I had taken pictures before I tried to fix it!   
On the other hand, it is the first point I have made that I would have been happy to claim as mine.  It was obsidian, and I did not snap it in half, so it was still a win.  Best I have ever done so far.