since it is a single crystal. It can be polish to very smooth finish with very low friction.Hardness and coefficient of friction of single crystal natural diamond dies vary with crystallographic orientation and results in increased die wear along certain crystallographic directions. Toughness is very poor for natural diamond as the diamond crystal has naturally weak points called cleavage planes where fracture occur easily .
http://www.natust.com/cnc-mach....ined-parts/stainless