Why do the diamond is the hardest substance on the earth ?

Image credit: m.economytimes.com

Diamond is made up of carbon and it is the hardest substance on the earth but the graphite is also made up of carbon then why is it one of the softest substance, 

Let's know why, 

Diamond and graphite both are the allotropes of carbon. Both are made up of the atoms of the carbon, but the types of atomic bonds between them is different which give rise to different material structure and properties. 

The outermost shell of each carbon atom has four electrons. In diamonds, these electrons are shared with four other carbon atoms to form very strong chemical bonds resulting in an extremely rigid tetrahedral crystal. 

Image credit: Wikipedia.org

This makes the diamond the naturallly strongest substance on the earth. 

Yes, Diamond the hardest substance but naturally because wurtzide boron nitride (synthetic) and lonsdaleite (which comes from meteorites) both are harder than diamond.

Now you understood that the diamond is the hardest substance but naturally and wurtzide boron nitride and lonsdaleite are harder than diamond but they are synthetics.

Comment your questions which you want to be answered.