Hardness
Customize the machine block breaking speed.
Hardness is a float value used to calculate the breaking speed of the machine block.
The higher the hardness the longer the breaking time.
The default hardness is 3.5.
A hardness of -1 will make the block unbreakable (like bedrock).
Some comparisons with vanilla blocks :
Wool : 0.8
Stone : 1.5
Dirt : 0.5
Obsidian : 50
Netherrack : 0.4
End stone : 3