Both coal and diamonds are forms of elemental carbon. Coal is brittle while diamonds are considered to be the hardest of all substances known. What is the appropriate justification for this?

Although coal and diamonds are both composed of carbons alone, they differ in their properties because of the bonds present in each substance. Diamonds are composed of covalent bonds which are strong and is crystalline in nature which makes it sturdier. Coal is amorphous which allows the slipping of irregular layers to each other making coal brittle