Diamonds may be losing their shine.

Retail sales of diamonds are slowing globally as a younger generation of consumers appears to be less attached to traditional diamond jewelry than their parents and grandparents, according to industry analysts.

"Millennial consumers have distinctive preferences, which in many ways diverge from previous generations," Bank of America Merrill Lynch analyst Ashley Wallace said in a research note this month. "They tend to be more value conscious, more concerned with sustainability and ethical production, and often value unique and individual products versus items that are standardized and mass-produced."



They are also marrying later. The median age for millennial women to marry is 27 and for men 29, according to Pew Research. That's a challenge for the diamond business.

The bridal category, including engagement or wedding ring purchases, represents as much as half of the total merchandise sold by some of the major U.S.-based jewelers.



And when they do marry, some consumers are opting for more gemstone engagement rings, such as sapphires, or fashion jewelry with lab-grown diamonds, according to industry analysts. Synthetic diamonds can cost 30 percent less than mined diamonds.

"Millennials don't want what all their friends have and don't want what they've been told to have," said Amanda Gizzi, a spokeswoman for Jewelers of America, a trade association with more than 8,000 member jewelers.



In an attempt to counteract the trend, the Diamond Producers Association, a global trade group of seven of the world's leading diamond producers, launched an advertising campaign to win over the hearts, minds and wallets of millennials. Its slogan is "real is rare, real is a diamond." This effort follows the relaunch last fall of the iconic "a diamond is forever" advertising by De Beers, the world's largest diamond marketer.