An engagement ring or a home down payment? Why some young couples are proposing with lab diamonds.

PHILADELPHIA — Years before Jasmine Ma and her fiancé, Ricky Chen, stepped foot into a jewelry store — before they had even talked seriously about marriage — Ma made one thing clear: She didn’t want a mined-diamond engagement ring. “If he was going to put his money toward this, I’d prefer he get something lab-grown,” she said. Not only would they be able to get a larger stone for less money, but she’d also feel better about the decision ethically, Ma said she told him, due to diamond mining’s history of human rights violations. The 27-year-old got her wish earlier this month when Chen dropped ...