Tom Zoellner, The Heartless Stone: A Journey Through the World of Diamonds, Deceit, and Desire

"... Her boyfriend gives her a Mercedes, [her friends] say, 'Oh, that's nice.' But her boyfriend gives her a diamond, they say, 'Oh, he's serious.' It's not just the gift of love-it's the gift of commitment. She's not jumping up and down because she got a diamond ring but because she got a guy! There are those who say you don't need diamonds. I say they're right. Just like you don't need sex."