Using a diamond saw, he sliced the ax parallel to the polished surface and then buffed the new surfaces with commercial polishing equipment using three abrasives: diamond, corundum, and quartz.

Researchers have uncovered strong evidence that the ancient Chinese used diamonds to grind and polish ceremonial stone burial axes as long as 6,000 years ago -– and incredibly, did so with a ...

Since corundum is the second-hardest mineral on earth, he concluded that the surface could only have been achieved by using diamonds as polishing agents.