The diamond industry is expected to grow in coming years on strong demand from China, India and the U.S., but there is a key hurdle ahead: millennials.

Speaking with CNBC’s “Street Signs” last week, Charles Rosario, senior vice president of Lazare Diamonds, reflected on the role the millennial generation — broadly defined as those born between the 1980s and early 2000s— will play in his industry.

“They are not the diamond market today, but they are the future,” he said.

But they already are putting some of their money into diamonds: De Beers’ 2016 Diamond Insight report said that in 2015, the millennial generation spent nearly $26 billion on diamond jewelry in the U.S, China, Japan and India combined.

Millennials represent a significant opportunity for the diamond industry, but have different shopping behaviors, and product interests. That suggests that dedicated marketing efforts are needed to target those customers effectively.

Rosario mentioned that “millennials are tech-savvy, well educated, and live on social media.” So, he said, the key strategy for marketing to millennials will be the “use of social media and the internet” by “understanding and following their tendencies, speaking their language and feeding them information that is aligned with their lifestyle.”

One of those products that may come up in millennials’ research is laboratory-grown diamonds, which are growing in popularity as the low profit margins in the cutting and polishing segment have heightened midstream players’ interest in non-natural varieties.

Jason Payne, co-founder of Ada Diamonds told CNBC that lab-made diamonds, compared to mined diamonds, “have fewer impurities and fewer defects in the crystal structure.” Furthermore, they are of “known origin” and they do not “harm ecosystems, wildlife, or watersheds.”

So who are the main buyers for lab-made diamonds? According to Martin Roscheisen, CEO of Diamond Foundry, those include customers who “are especially concerned about ethics and environmental costs” and those who are “less romanced by the idea that a diamond needs to come from under the earth.”

Those characteristics may well overlap with insights into millennial consumers, and the diamond industry is aware: Rosario told CNBC in an email that he considers the generation environmentally conscious and “they research products of interest before buying and are socially responsible.”

So as consumer tastes change, and younger generations achieve more buying power, laboratory-grown diamonds might emerge as a competing category to mined diamonds.

But the natural diamond industry isn’t sitting idly by as the market shifts.

To increase the attractiveness of their product, key industry players have formed the Diamond Producers Association, which came up with the “Real is Rare” campaign to highlight the emotional appeal of natural stones.

Rosario, for his part, said lab-made diamonds “may eventually challenge the smaller, lowest-quality natural diamonds for a place in the market.”

In fact, both types can “absolutely” co-exist, according to Paul Zimnisky, an independent diamond analyst based in New York.

“They are essentially different product classes,” he said, explaining that he thinks lab-made diamonds will be more of a “niche product class” with their largest market being a use in high-tech applications.