Why does graphite leave a dark mark on paper?

Graphite leaves a dark mark on paper due to its unique crystal structure, which consists of parallel, widely spaced layers of carbon atoms.12

Within each layer, carbon atoms are arranged in fused hexagonal rings held together by strong covalent bonds. However, the bonding between these individual layers is much weaker, relying on van der Waals forces rather than strong localized bonds. Because these layers are not tightly bound to one another, they can easily slide past each other, a property that contributes to the material's softness and lubricity. When you press a pencil against paper, these layers of carbon atoms shear off and adhere to the surface, creating the characteristic dark mark.12