Book excerpt: In 2000, Tom Zoellner purchased a diamond engagement ring and proposed. His girlfriend said, "yes" and then, suddenly, walked out of his life making Tom the owner of a used engagement ring. Instead of hitting the self-help shelves of his local bookstore, he hit the road travelling to diamond mines in Africa, Canada, India, Brazil and Russia to discover the true worth of this shining gem. He travelled to Japan to understand how diamonds were linked with engagements and delved into the history of our own American romance with the diamond ring. He gained entry to DeBeers, the London diamond merchants. He visited shopping mall jewellers with starry-eyed couples. Through all of his travels, he searched for an answer to the question "How has one stone created empires, ruined lives, inspired lust and emptied wallets throughout history?" A diamond version of Susan Orleans's The Orchid Thief, Tom Zoellner's The Heartless Stone is a journey to the cold heart of the world's most unyielding gem.