Types of Carbon
Carbon is found in two forms - (1) crystalline (crystal-forming) and (2) amorphous (shapeless). Crystalline atoms are arranged in an order. Diamond and graphite are two forms of carbon.
Each atom of the carbon in the diamond is attached to the other four carbon atoms by the attraction force. Diamonds have a three-dimensional (solid) structure. Due to this firm structure, the diamonds are very hard substances. The diamonds are found about 150 km below the surface of the earth where the heat and pressure are very high.
The carbon atoms in graphite are arranged as layers (one above the other). The force between these layers is less. This can cause the layers to slide over each other. Hence graphite is soft and smooth to touch.