How are diamonds formed ?

Inside the earth’s crust, under deep pressure and heat, carbon atoms crystallize to form gemstones which come out of the crust during the deep source volcanic eruptions bringing diamonds to the surface.  

The diamond structure is made from the covalent bonding between atoms where the atom gets the crystalline structure as each carbon atom is linked to 3 other carbon atoms that create a strong, stable lattice.

Most diamonds are formed inside the mantle under the continental crust, where they get a stable environment to grow to become the strongest substance on earth before they are pulled out from the kimberlite pipes by the companies that mine diamonds.

As per the natural processes, the tectonic plates collide, and the massive land is forced underneath into a subduction zone. If the plates carry rocks rich in carbon, it melts in high heat and pressure to form diamonds.

Some asteroids hitting the earth's surface bring explosions, and the carbon made deposits turn into tiny gemstones instantly.