It’s the ultimate in understated luxury: A diamond as thin as a shard of glass and as smooth as ice. It’s so discreet and minimalist that some people may not recognize it’s a diamond. But the portrait cut diamond is a perfect stone: Billions of years in the making, it’s precision cut without any visible inclusions. It’s pure magic.

For style-setters like Kendall Jenner and Blake Lively, who have been spotted in designer Lorraine Schwartz’s signature portrait cut diamond rings, it’s a confident expression of their individuality. Who cares if nobody knows that 12-carat stone on your finger is an exceptional diamond? For the actress Rooney Mara, who wears a demure portrait cut diamond engagement ring, it reflects her understated style.

“It’s old-school but it’s modern and chic,” says Lorraine Schwartz of the portrait cut diamond, which has its roots in ancient India.

 “My clients already have traditional diamonds, and the portrait cut is unique, elegant and beautiful,” says Schwartz. “It’s super sophisticated.” It happens to be the designer’s favorite too.

More designers are taking notice of these sleek diamonds and are creating portrait cut diamond jewelry in all shapes, sizes, and prices.

It’s also a new favorite engagement ring for women and men who want a diamond, but don’t want high sparkle. For some, it’s their diamond secret.

Here are 7 things to know about portrait cut diamonds (and why you need to add one to your jewelry wardrobe):

1. It’s one of the oldest diamond cuts – and it has a fabulous backstory

One of the earliest diamond cuts, the portrait cut was a favorite of the celebrated Mughal Emperor Shah Jahan. He’s the one who had the legendary Taj Mahal built (1631-1648) in memory of his beloved wife Mumtaz Mahal. The emperor was also sentimental about his jewels: He had transparent thin diamonds placed over hand-painted portraits to protect and enhance the wearable miniature art. Hence the name portrait cut.

2. Its minimalist beauty appeals to art lovers

The flat portrait cuts give designers like Vishal Kothari of Vak jewelry the ability to create artistic designs without traditional heavy metal settings. “The diamonds literally look like they are floating on the skin when you wear them,” he says. “It’s a unique and modern interpretation of an old-world that appeals to art lovers.”

3. It appears simple but demands precision craftsmanship

The portrait cut requires top-quality rough stones and precision master cutters to achieve the ultra-thin, clean diamond cut. Vak works exclusively with a family of Indian diamond cutters who specialize in portrait cuts. He says, “Because it’s a transparent stone, you need to start with essentially flawless diamonds.”

4. A lover’s secret diamond

In the 19^th century, women and men wore a miniature likeness of their lover’s eye hand-painted on a ring or locket and covered it with a portrait cut diamond. It was a way for secret lovers to feel close even when apart. The Canadian jeweler Kelty Pelechytik continues that tradition in her own style. She enlisted Australian artist Robyn Rich to paint bespoke miniature lovers’ eyes on gold, and the jeweler covers them with a portrait cut diamond set in contemporary gold rings and pendants.

5. It’s a diamond engagement ring for non-conformists

Not everyone wants the sparkle of a faceted diamond, but they still want an engagement ring with the tradition and lasting heirloom quality of a diamond. The flat portrait cut is the new alterative engagement ring.

“People want unique, individual diamond rings that represent who they are and these cuts, which come in odd shapes, are cool and unique,” says Pelechytik. She presents a range of handmade portrait cut engagement rings and wedding bands in off shapes starting at just a few thousand dollars.

Read More: Engagement Ring Styles and Settings

6. For diamond lovers who have it all

For Vishal Kothari’s wealthy clients who already own large, faceted diamonds and fancy colored diamonds, the portrait cut is something new and fresh. “My clients are intrigued by the portrait cut because it is beautiful in its simplicity and different,” he explains. The designer’s Art of Heaven pieces combines portrait cuts with rubies and emeralds, which he says enhances the deep colored gems.

7. Everyone’s favorite new diamond cut

Designers love the lightweight portrait cuts because they don’t require heavy metal settings. That means designs are light, subtle – and its jewelry you live in. Vak’s new Waterfall earrings, for example, feature four rows of draping portrait cuts diamonds. They are light and breezy just like his new line of bracelets and necklaces made with the appearance of floating diamonds. “These simple pieces with smaller stones are for the younger generation of women,” he explains.

Whether your style is big diamonds (Lorraine Schwartz has several portrait cuts 10 carats and larger) or everyday diamond jewelry, you can expect to see more portrait cut diamonds. They may be discreet but if you know, you know.