unhybridised ‘p’ orbitals interact to form a π system which is delocalised
  over the whole layer. The interactions known as London dispersion forces
  between the layers which are separated by a distance of 3.35 A⁰are weakened
  by the presence of water molecules so that it is easy to cleave graphite.
  For this reason graphite is used as lubricant and as the ‘lead’ in pencils. 
       
  • How do you understand the markings (writings) of a pencil on a
    paper?
    
         When we write with a pencil, the interlayer attractions breakdown
   and leave graphite layers on the paper. Pencil marks are easy to remove
   from paper with an eraser because, the layers do not bind strongly to the
   paper. Graphite is a good conductor of electricity because of the
   delocalised         π electron system.      
            
   Buckminsterfullerene (C60)        
            
         Buckminsterfullerenes are molecules of varying sizes that are
  composed entirely of carbon. The arrangement of these molecules leads
  to the form of a hollow sphere, ellipsoid, or tube depending upon their
  orientations. Fullerenes are formed when vaporized carbon condenses in
  an atmosphere of an inert gas.  
            
        
      
      Buckyballs:  Spherical fullerenes are also called buckyballs. 
      Buckminsterfullerene (C60) contains nearly spherical C60 molecules
   with the shape of a soccer ball.