New York’s Diamond District is set to sparkle on TV this Tuesday night in the documentary series Streets of Dreams with Marcus Lemonis.

The series presenter is a self-declared “champion of entrepreneurs” who is seeking to discover what makes America’s most famous streets tick. As Lemonis walks amid the hustle and bustle of hawkers and diamond dealers on 47th Street, he has one clear goal: to discover how diamonds are priced. He ventures behind the jewelry counter “to crack the code on this notoriously secretive industry.”

Entering the International Gem Tower, Lemonis sits with Reuven Kaufman, president of the New York Diamond Dealers Club (DDC). The fact that the word “mazal” still binds deals —with no lawyers or signatures — astounds the show host.

“Somehow, this archaic system works,” says Kaufman to ease the look of disbelief on Lemonis’s face.

The action quickly moves from the DDC’s trading floor to street level and veteran diamond dealer Fishel Beigel.

“How do I know I am getting a good deal?” asks Lemonis.

“You are never going to know,” says Beigel. “There’s no such thing as knowing 100%. You have to trust me. It’s built on trust. It’s built on who I am. It is built on my reputation. And my culture. You have to trust me.”

The perplexed Lemonis muses, “I want to change this street to Trust Avenue. For outsiders, the number-one concern is trust. The number-one word they are trying to sell us on is ‘trust.’ So far on this block, ‘trust me’ is the only business advice I’ve been given. But to me, it’s just a nice way to hide a total lack of transparency.”

He eventually walks 47th Street with Martin Rapport, whom he calls “the Wizard” after learning about the Rapaport Price List and the role it played in bringing greater transparency to the diamond trade in 1978.

Over four decades later, the Rapaport Group chairman’s enthusiasm is still a match for the electricity of the Diamond District.

“There’s something else that’s going on in America that’s amazing — the greatest new business for the jewelry industry,” Rapaport tells Lemonis. “There are 97 million Americans that are baby boomers or older. What’s going to happen to the jewelry? They say a diamond is forever, but little old ladies are not necessarily forever.”

He believes Rapaport Auctions offers a solution by enabling people to trade estate jewelry for fair market value.

Finally, Lemonis considers for a moment what will take center stage in engagement rings in the future. “It will stay the diamond,” he says confidently. “You know why? Because they are pretty damn good-looking!”

Watch Streets of Dreams with Marcus Lemonis featuring 47th Street on Tuesday, December 29, at 10 p.m. ET on CNBC.