Explanation:

Graphite is structurally composed of planes of polycyclic carbon atoms that are hexagonal in orientation. The distance of carbon atoms between planes is longer and therefore the bonding is weaker. Graphite is best suited for lubrication in air.
It is a mineral made of loosely bonded sheets of carbon atoms, giving it a slippery texture that makes it a very effective lubricant. This slippery quality also makes graphite a good material for pencil lead because it easily sloughs off onto paper.
Graphite is bonded by covalent bond, thus, it is helf by weak intermolecular forces. Since it has weak intermolecular forces, graphite would be slippery and soft enough to act as a lubricant.