The strongest thing on earth

While yes,diamond is very tough,it has many points that if hit,will cause it to fracture.

Laughs because of graphene and carbyne

Breaking one is easy. Then, it's just a matter of force. Cutting it is hard. Generally, to cut diamond, they use another diamond, a laser, or a diamond tipped saw.

Diamond's cannot be scratched or scuffed on their surface easily. You could break a diamond with a hammer if you wanted to, since their hardness makes them very brittle. Cutting a diamond is the hard part, smashing one with a rock is not. Jade is far more resilient to abrasive force than a diamond is, despite being twenty times softer.

Then how do you break a Nokia?

Lasers

Diamond is NOT the "strongest" material on Earth, it IS the "hardest". There's a big difference.

Its hard, but brittle. Think of diamond as super glue and steel as epoxy. If you glue 2 pieces of steel together w super glue and hit it off something, the glue will crack. If you do the same with epoxy, it has equal strength, its more likely to flexor epoxy can be melted, to be reshaped, unlike super glue. Science