The rapper (real name: Colson Baker) and actress opened up to Vogue this past weekend in Milan amid their attendance at the Dolce & Gabanna fall 2022 menswear show, where Kelly, 31, noted that his new fiancée's custom two-stone ring includes "bands [that] are actually thorns."
"So if she tries to take it off, it hurts," added the "Bloody Valentine" musician, quipping, "Love is pain!"
Of Fox's unique jewelry, Kelly said, "It's a thoroughbred Colombian emerald, with no treatment. It was just carved into the teardrop, straight out of the mine. And the diamond was directly from [jeweler] Stephen [Webster]."
"The concept is that the ring can come apart to make two rings. When it's together, it's held in place by a magnet," he continued. "So you see how it snaps together? And then it forms an obscure heart."
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Alongside his engagement announcement last week, Kelly shared an up-close video of the gorgeous emerald and diamond sparkler he had custom-made by Webster for the occasion.
In the video, the pear-cut stones shimmer as the Transformers actress, 35, moves her hand. In the caption of his post, the Born with Horns artist explained the design choice.
Machine Gun Kelly/Instagram. Inset: getty
"I know tradition is one ring, but i designed it with Stephen Webster to be two: the emerald (her birth stone) and the diamond (my birth stone) set on two magnetic bands of thorns that draw together as two halves of the same soul forming the obscure heart that is our love," he wrote.
Webster told PEOPLE exclusively of the design, "By the use of magnets buried within the gold, [the rings] are attracted to each other and sit together perfectly on the finger," says Webster. "[It's] a detail that is both modern and quite extraordinary."
While Webster didn't disclose the cost of Fox's engagement ring, diamond experts estimate it could be worth up to $500,000.
Jewelry designer Mark Broumand said, "This Toi et Moi [you and me] style has a very unique look. The gorgeous white diamond and green emerald really compliment each other. They indeed look to be top quality, putting the ring cost around $300,000."
Sahar Manley, owner of jewelry label Camilla Seretti, thinks it could be worth a bit more.
"It appears that each gemstone is 7 carats, which would make the ring valued at nearly $500,000," Manley said. "Enlisting an expert like Stephen Webster to perfect the custom ring was a smart and thoughtful move to truly master the piece."