Rock does not yield to force. It yields to something harder than itself, turning fast enough to grind quartz into flour. That is the entire premise of diamond drilling, and it is why almost everything we know about the crust beneath us arrived at the surface inside a hollow tube. A core bit is annular. It cuts a ring rather than a disc, leaving an intact cylinder of rock standing in the middle, which is captured in an inner barrel and lifted out. Rodolphe Leschot patented the idea in 1863 while tunnelling through the Alps, setting carbonado, natural black diamond, into the crown of a rotating pipe. The geometry has barely changed since. What changed was the diamond itself. Tracy Hall and the General Electric team synthesised the first reproducible stones in December 1954 at roughly 10 GPa and 1600 degrees Celsius, and abrasive grit became an industrial commodity rather than a Brazilian import. Modern impregnated bits are built around that grit: - Synthetic diamond is dispersed thro...