https://www.theatlantic.com/magazine/archive/1982/02/have-you-ever-tried-to-sell-a-diamond/304575/ What is the worst "investment" you can make? Diamonds, is what. You're guaranteed to lose money buying those industrial drill bits which are now marketed as some symbol of love, romance and permanence. (Bonus: like cars, diamonds lose most of their value once they are bought [you simply will not find a buyer or a decent price for most gem-quality diamonds], and their correlation with relationships is the world's most successful marketing scheme)