Many common materials such as water, wood, plants, animals, diamonds, fingers, etc. are usually considered to be non-magnetic but in fact, they are very weakly diamagnetic.
Diamagnets repel, and are repelled by a strong magnetic field.
The electrons in a diamagnetic material rearrange their orbits slightly creating small persistent currents which oppose the external magnetic field. Two of the strongest diamagnetic materials are graphite and bismuth. The forces created by diamagnetism are extremely weak, millions of times smaller than the forces between magnets and such common ferromagnetic materials as iron. However, in certain carefully arranged situations, the influence of diamagnetic materials can produce startling effects such as levitation. It was proved in 1842 that it is impossible to stably levitate any static array of magnets by any arrangement of fixed magnets and gravity.