Pliny moves into crystallography and mineralogy, describing the octahedral shape of the diamond and recording that diamond dust is used by gem engravers to cut and polish other gems, owing to its great hardness. He states that rock crystal is valuable for its transparency and hardness, and can be carved into vessels and implements. He relates the story of a woman who owned a ladle made of the mineral, paying the sum of 150,000 sesterces for the item. Nero deliberately broke two crystal cups when he realised that he was about to be deposed, so denying their use to anyone else.