If diamond is the hardest rock on earth (and hard by definition is solid, firm, and resistant to pressure; not easily broken, bent or pierced), and it can break with a hammer
![Yosemite's El Capitan: Free climbers reveal they used 'positive thinking' to beat world's toughest cliff | The Independent | The Independent Yosemite's El Capitan: Free climbers reveal they used 'positive thinking' to beat world's toughest cliff | The Independent | The Independent](https://static.independent.co.uk/s3fs-public/thumbnails/image/2015/01/15/19/El-Capitan-2-v2.jpg)
Yosemite's El Capitan: Free climbers reveal they used 'positive thinking' to beat world's toughest cliff | The Independent | The Independent
![Surface of rocky wall with different hardnesses where the parts of the hardest rock stand out, forming slienties. Can be used as background Stock Photo - Alamy Surface of rocky wall with different hardnesses where the parts of the hardest rock stand out, forming slienties. Can be used as background Stock Photo - Alamy](https://c8.alamy.com/comp/TX45XP/surface-of-rocky-wall-with-different-hardnesses-where-the-parts-of-the-hardest-rock-stand-out-forming-slienties-can-be-used-as-background-TX45XP.jpg)