Nine floors above the storefronts of New York’s diamond district, in a corner suite of the World Diamond Tower, a lariat necklace with diamonds the size of molars sat inside a silver briefcase. The necklace was fresh from a cleaning — an ultrasonic water bath, followed by a steam — and visiting the office of the jewelry designer Alex Moss in late January en route to its owner: the rapper and singer Drake.

“Jewelry is like a car, it needs to be maintained,” Mr. Moss, 30, said.

The piece, created by Mr. Moss, took 14 months to make. A video shared on Instagram by the designer said that its 42 diamonds represented the number of times that Drake had considered proposing marriage. When asked how much the necklace cost, Mr. Moss declined to answer, citing the security of its owner.

Personal orders like Drake’s necklace have been Mr. Moss’s bread and butter since he started his namesake line in 2020. Last year, he created about 170 custom pieces, he said, and is currently juggling about 40. Much of that jewelry has been made for young hip-hop artists: His other clients have included include Tyler, the Creator, ASAP Rocky and Chief Keef. Some of the pieces have had price tags with six figures, including a belt set with rubies and white, black and green diamonds for ASAP Rocky, and a diamond-and-sapphire-encrusted bellhop chain for Tyler, the Creator.

“The artists I look up to went to the Ben Ballers, to the Jacobs, to the Lorraines,” said Tyler, the Creator, referring to the jewelry designers Ben Yang, Jacob Arabo (a.k.a. Jacob the Jeweler) and Lorraine Schwartz, all of whom have been recognized for blinging out hip-hop stars. “Now we have Alex Moss.”

‘I Can Do This’

This month, Mr. Moss is expanding his business with the introduction of a new collection of ready-made jewelry sold on his website. Starting at about $1,000, the pieces are by no means cheap, but they cost less than his custom designs. “There is a huge range,” he said.

The collection, called “Cathedral of Dreams,” borrows heavily from Christian and gothic imagery. There are pieces shaped like crosses, crucifixes, angels and the face of Jesus wearing a diamond-studded crown of thorns. “I’ve always loved the aesthetic,” said Mr. Moss, who was raised in the Armenian Orthodox Church.

“I’m faithful,” added Mr. Moss, who was puffing on a strawberry kiwi vape and wearing three of his line’s chain necklaces, as well as a tongue-shaped “Lick of Death” ring from his new collection. “But I am not the most religious person.”

Mr. Moss, who is from a suburb of Toronto, said he was obsessed with “Star Wars” and downloading hip-hop music from the Napster successor Kazaa when he was growing up. As a tween, he nurtured his creativity through Adobe Photoshop, which he learned to master himself. Using money he had saved, some made from reselling sneakers on eBay, he started a streetwear line called Bandit in his senior year of high school, before dropping out. A self-described “troublemaker,” Mr. Moss then had jobs as a waiter, a paralegal assistant and at a Bed Bath & Beyond store while working on his streetwear line.

In 2016, after earning his high school equivalency diploma in Canada, he moved to New York at 25 to study fashion at Parsons School of Design.

“It wasn’t a typical path,” said Mr. Moss, who is 6 foot 5 inches and has wavy shoulder-length black hair and a black goatee. “Me being 25 and all of these kids are 18.”

While at Parsons, he got an internship at the jeweler Avianne & Co. in Midtown. (Its office is a few doors down from Mr. Moss’s suite in the World Diamond Tower.) He developed an interest in jewelry through his love of hip-hop, he said, and as an intern, he would help design custom pieces.

“I was like OK, I’m actually sick. I can do this,” Mr. Moss said. Eventually, he dropped out of Parsons to work on custom design projects at Avianne & Co.

He had already worked on some personal orders for hip-hop artists by the time the rapper Playboi Carti introduced him to ASAP Rocky while the men were in Paris for Virgil Abloh’s debut men’s wear show for Louis Vuitton in 2018. “I thought he was a rapper the first time we met,” ASAP Rocky said. Of Mr. Moss’s jewelry, he added: “It’s less about the flex than the artistic value.”

When Mr. Moss started his namesake line in 2020, he was working from his apartment in the Long Island City section of Queens. At the time, he had saved enough money to cover rent and living expenses for a couple of months, he said. Two weeks later, New York implemented its pandemic lockdown.

“Who was going to buy jewelry?” Mr. Moss recalled thinking at the time. “No one even knew where we were getting food from.”

Early six-figure custom orders, including from the rapper Jack Harlow and the music producer Rvssian, kept his business afloat, he said, and enabled him to set up shop at his diamond district location.

A Desire to Be Attainable

From Mr. Moss’s office overlooking 47th Street, the glimmering red lights of Times Square look a bit like shimmering Burmese rubies. Inside, there are rocks both real (diamonds in jewelry display cases, green marble on walls) and fake (in one nook, walls were treated to look like a cavern, or “diamond cave,” as Mr. Moss called it).

In another corner are a Pac-Man arcade game and a vending machine that Mr. Moss hopes to one day fill with branded trinkets. “Key chains, ashtrays, things you can only get here,” he said.

His office and showroom are a few floors above the factory where his line’s pieces are made, a space that Mr. Moss had previously used as his first office in the World Diamond Tower. (“He’s moving on up, like George Jefferson,” as ASAP Rocky put it.) The factory is made up of two lab-like rooms where a head jeweler oversees a team of three diamond setters as they place stones and laser precious metals.

Mr. Moss, who employs 15 people, is quick to point out that the artisans in the factory are the “jewelers” who construct his pieces, and that he is the “jewelry designer” who conceives them. “I’m like Ralph Lifshitz,” Mr. Moss said, referring to the founder of Ralph Lauren, who built an empire not on sewing expertise, but on creative vision.

In discussing the future of his company, Mr. Moss mentioned aspirations for it to follow the trajectory of Chrome Hearts, which over the years has evolved from a niche line to a lifestyle brand, in part because famous musical artists (Cher) and models (Bella Hadid) have helped popularize its silver jewelry, hoodies and T-shirts.

“Chrome Hearts is attainable,” Mr. Moss said. “That is the direction we are going in.”

He is working on renderings for a watch he hopes to start producing in partnership with a watchmaker in the coming years. Though Mr. Moss has customized vintage Cartier and Rolex watches — a process he calls “Frankensteining” — he has yet to design his own timepieces.

He also wants to open a flagship store and showroom in SoHo. Though his business has flourished in the diamond district, there are associations with the neighborhood that could become limitations to additional growth, Mr. Moss said.

“A lot of jewelers in our space, they are like Chris the Jeweler, Jacob the Jeweler,” he said. “I’m not Alex the Jeweler. We are Alex Moss New York.”