Diamond Hardness vs Toughness

Diamond is not only one of the most expensive gemstones, but it's also the strongest one. Diamonds are believed to bond people together and bring emotional and mental clarity. 

Hardness 

Mohs’ Hardness Scale 1 – 10 charts the relative hardness of the various minerals: Talc-1-softest to Diamond-10-hardest. Since hardness depends upon the strength of the bonds between atoms in a crystal, there can be variations in hardness depending upon the direction in which one measures this property. Diamonds (hardness 10) show a variation in hardness. The octahedral faces are harder than the cube faces, translated diamonds vary in hardness. 

Toughness Scale

A mineral’s toughness is its ability to resist being fractured. Toughness means resistance to breaking, chipping or cracking in general, how well a stone holds up under mechanical stress, such as impact from a fall. Toughness Scale: Exceptional, Excellent, Good, Fair, or Poor. 

Diamond is formed in the cubic crystal system and has 4 perfect cleavage directions. A cleavage direction is the weakness plane in the molecular crystal of a diamond. Hence, an experience diamond cutter will look for the cleavage plane to cleave a big diamond.