To Mbuyi Mwanza, a 15-year-old who spends his days shoveling and sifting gravel in small ... notoriety surrounding so-called blood or conflict ­diamonds—precious stones mined in African war ...

Amid a plummeting stock market, self-driving cars running amok, and Mark Zuckerberg buying a house in Northwest, another sign of end times has arrived in Washington, DC: A diamond, the color of blood.