DIAMOND is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, diamond has the highest hardness and thermal conductivity

of any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools.

AT THE BEGINNING of this century a famous and very expensive diamond was stolen from a museum in France. The police worked hard to find the thief but they were not successful. Everybody thought that the diamond could never be found again.

One day, however, a girl who worked in a hotel in Paris saw an apple lying on the table in the room of a guest. The guest was out and she was so hungry that she just could not help biting the apple. As she did so, she felt a very hard object in her mouth. It proved to be the stolen diamond. She gave the precious stone to the police who returned it to the museum.