Millennials are killing all kinds of things. The decline of casual dining chains, paper napkins and home ownership are all being blamed on those born since the mid-1980s.

Even diamonds, one of history’s most prized stones, aren’t selling like they did for previous generations.

Online retailer Brilliant Earth is trying to appeal to millennials by focusing on something many of them care about, the ethical sourcing of products. In this case, the online retailer is selling diamonds in customized settings that it says are not “tainted by violence, human rights abuses, poverty, and environmental degradation.”

“We conducted a survey that showed that 80% of millennials believe it’s important to purchase responsibly sourced jewelry, which is a higher percentage than other demographics,” says Kathryn Money, vice president of strategy and merchandising at Brilliant Earth. “We’re finding that millennials care about where and how their products are sourced.”

Beth Gerstein and Eric Grossberg founded Brilliant Earth in 2005 as a place to shop for conflict-free jewelry, with the goal of offering a selection as varied as that found at traditional jewelry retailers.

“Customers are really seeking products that express their individuality and are increasingly drawn toward uniqueness in their products,” Money says. “We’re seeing that manifested in a few different ways, like choosing a distinctive ring setting or using colored gemstones in lieu of a diamond, using a fancy non-round diamond and opting for rose gold or other metals.”

In addition to sourcing diamonds and gemstones from “beyond conflict free” sources, the company uses recycled precious metals in its rings and donates 5% of its profits to mining communities.

After years of online growth, Brilliant Earth has expanded its physical presence. The company opened its first physical store in San Francisco shortly after its founding and recently opened six more stores in locations including Denver, San Diego and Washington, D.C.

The new stores allow customers to see and feel Brilliant Earth’s products before buying them, and they highlight the company’s mission.

“The physical showrooms enable our customers to have a deeper and more tactile experience with our products and brand, which is especially important with a considered purchase like jewelry,” Money says. “Typically, customers are coming in for an hour and meeting with a jewelry specialist to learn about our sourcing practices and view our collection.”

However, e-commerce remains at the center of Brilliant Earth’s business. In fact, physical stores drive many sales to BrilliantEarth.com where shoppers can customize their jewelry in many ways.

For shoppers who can’t make it to a store, Brilliant Earth’s website provides 360-degree product views and also lets shopper see how jewelry looks on various skin tones. The site also provides a custom ring-building tool, letting buyers pair ring settings and metals with the diamond they want to use.

But the heart of Brilliant Earth’s appeal is its ethical sourcing. The company’s diamonds, in addition to being certified as conflict free by regional auditors, also meet standards tied to working conditions and environmental impact. Additionally, recycled stones and metals help cut down on the need for new materials, and turning to lab diamonds avoids mining altogether by producing the in an industrial setting using pressure.

Brilliant Earth competes online with the likes of Blue Nile, No. 96 in the Internet Retailer 2017 Top 500, and JamesAllen.com (No. 140), which also targets millennials. That strategy and target audience are what drew Signet Jewelers Ltd. (No. 113) to pay $328 million to buy JamesAllen.com parent company R2Net, in a deal announced Thursday. Millennials are the dominant age group targeted by both companies. Meanwhile, more established brands like Tiffany, No. 143, are investing in e-commerce to prop up slowing jewelry store sales.