Chocolate diamonds weren't always valuable. Here's how they went from cheap rocks to adorning Rihanna's $130,000 Grammys necklace.

• Chocolate diamonds are brown diamonds that are not too dark and not too light in color.
• Brown diamonds weren't popular in jewelry until the 2000s.
• Le Vian trademarked "chocolate diamonds" in 2000 and now the stones are popular in jewelry worn by celebrities like Rihanna and J.Lo.
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Following is a transcript of the video.

Narrator: Rihanna wore a $130,000 chocolate diamond necklace to the 2018 Grammys. And these Chocolate Diamond earrings that J-Lo likes to borrow: just over $16,000, but it wasn't that long ago when brown diamonds would have never made the red carpet, selling for six times less than they do today. So what changed? Why are Chocolate Diamonds so expensive?

Diamonds get their color by how they're formed, whether it was a different element that got pulled into the carbon structure. Like boron, which gives diamonds a beautiful blue hue, or maybe it was close to a natural source of radiation, making them appear green. Whatever the reason, diamonds come in a rainbow of bright, beautiful colors, and then there are brown diamonds. For centuries, brown diamonds were cheap. They were typically low in quality and had lots of imperfections. So jewelers didn't want them, especially when they could use brighter pink, blue, or yellow diamonds.

Instead, brown diamonds were used as tools to drill through rocks and cut glass. But in 1986, Argyle Mine opened. Today, it produces more diamonds than any other mine in the world. Most of them being brown diamonds. And while it's been said that the quality of Argyle stones is not equal to their quantity, companies have still managed to find a market. One company in particular being Le Vian Corp.

Eddie LeVian: We found these beautiful, natural fancy color brown diamonds that were coming out of the Argyle Mine of Australia that were quite underappreciated.

Narrator: That's Eddie LeVian. He's the CEO of Le Vian Corp. Le Vian trademarked the name Chocolate Diamonds in 2000, giving it a monopoly on the market for these particularly named brown diamonds. Soon after this rebranding, Chocolate Diamonds took off. Google searches for "Chocolate Diamond" went from virtually zero in 2007 to 400,000 in 2014. And the more popular they became, the more value they earned.

Eddie LeVian: The price of Chocolate Diamonds has risen more than three-fold in this period of time.

Narrator: In the '80s and '90s, gem-quality brown diamonds were worth about $1,500 per carat, but now many sell for up to $10,000 per carat. And the price of larger stones has risen even more, by as much 25 times. Le Vian isn't the only company that has tried to rebrand brown diamonds. Jewelers like Zales have called them other names like Champagne, Cognac, and Cappuccino, but Chocolate was the name that really took hold. Given its success, we asked Eddie how the name came about.

Eddie LeVian: The name of Chocolate many people think, "Oh, yeah because these are brown, so they put chocolate," but the reality was there was a friend of mine, Bill Furman, who used to come every day after work and visit me, and he would always bring me artisan chocolates, and he would always talk about the special powers of chocolate, how it's health benefits, how it's an aphrodisiac, and I started to understand how chocoholics are passionate to the food chocolate. And so when we did the branding of Chocolate Diamonds, we really intended to tie in to the passion that people have, the obsession that people have to the food chocolate.

Narrator: Le Vian says just four percent of brown diamonds meet its criteria. The diamond needs to fall within a specific shape between C-4 and C-6 on the industry's color scale. So more like a milk rather than a dark chocolate. Once the right stones are ready, it's time to make jewelry, which ups the total cost. To get a closer look, we visited the jewelry company Suna Bros of NYC.

John King: Many years ago, diamond cutters began to experiment with different ways of placing the facets on these diamonds so that they didn't appear overly dark, and it allowed light to penetrate and reflect back, which gave all of these wonderful sensations.

Narrator: But Chocolate Diamonds may become harder to come by in the near future. There's been talk that Argyle Mine is running out of diamonds. However, John doesn't think that will stand in the way of their growing popularity.

John King: It would seem even at a point where Argyle may no longer be mining, that the groundwork has been laid, that the interest in a range of colored diamonds now exists, and certainly that for brown diamonds I think will sustain and probably only grow more.