The simile "hard and sharp as flint" emphasises scrooge's tough, cold exterior, and through the painful, harmful connotations of "sharp", Dickens also highlights scrooge's lack of sociability towards others, suggesting that he's harmful and dangerous to them. However, Scrooge being likened to "flint" suggests that, although he has never given "generous fire" he has the potential to be good-willed, sociable, generous and the other attributes encapsulated by the Christmas spirit, as portrayed by the recurring symbol of "fire" used by dickens to represent these values.