Guthrie, the mother of “Today” show host Savannah Guthrie, was abducted just as the Tucson gem shows were starting.
Remembering Pete Yantzer for His Contributions and His Kindness
Pete’s boundless curiosity extended beyond diamond cut and he was always eager to share his knowledge with others, no matter the topic.

I was reminded of this last month when I was writing about Terry Chandler’s retirement after 40 years, and again this week when I learned of the passing of George Peter “Pete” Yantzer, ECGA.
Pete started in the jewelry industry in the early 1970s, the seventh gemologist on staff at the Gemological Institute of America’s lab in New York City.
When I came into the industry in 2007, I knew him as the executive director of American Gem Society Laboratories, a role he held from 1996 until his retirement in 2015.
At AGS Labs, Pete was instrumental in developing the AGS Light Performance Cut Grade, a service that helped the entire industry better understand how light performs inside of a diamond, and how a better cut could lead to a prettier stone.
“It’s because of Peter that diamonds began to be cut better, with more exact proportions,” said Cathy Calhoun, a longtime AGS jeweler and one of his closest friends in the industry.
The service was so popular among jewelers that when AGS closed its lab in 2022 and merged with GIA, questions about the future of the AGS cut grade and light performance featured prominently on the list of FAQs AGS provided for its members.
In a statement shared by AGS, Jason Quick, Pete’s longtime mentee at AGS and now senior director of cut grade research at GIA, said Pete often spoke glowingly about the gemological giants who mentored him, legends like Richard T. Liddicoat and Bob Crowningshield.
For younger gemologists, Pete was their Richard Liddicoat and Bob Crowningshield.
“Beyond Pete’s pioneering gemological contributions, it will be his contagious smile, caring heart, and brilliant inner light that will continue shining on in the memories of those of us fortunate enough to have known him,” Quick said.
Pete was, above all, a kind and intelligent man and like so many intelligent people, he was insatiably curious.
As a journalist, I can tell you that these are the best kinds of people to interview.
More than a decade ago, Pete took the time to talk with me for an article I was writing on the controversies surrounding the grading of older diamonds.
In the story, I wrote that he is “one of a handful of people who can deliver an oral history on diamond cutting almost entirely off the top of his head,” and he did.
He walked me, then a still somewhat-green jewelry journalist, through the timeline, starting before the patenting of the first steam-driven bruting machine in 1874.
Cathy describes Pete as “sheer genius.”
“He delved into everything, no matter how small.”
She recalled her friend of almost 40 years going down the rabbit hole on dog treats—Beggin’ Strips, to be exact—for his beloved pup, Chewy.
Most people would just absentmindedly open the bag and give their dog a treat whenever, but not Pete.
He researched ingredients and calorie counts to calculate exactly how many treats Chewy should consume, a move that was “typical Peter,” Cathy said.
Outside of dog treats, he had a passion for photography.
Diane Vunic with Suna Bros. recalled Pete giving her tips on taking pictures during a trip to The Butchart Gardens on Vancouver Island during AGS Conclave 2002.
“Not only did Peter encourage me to go on the trip, but he inspired me to start photographing the small details in each flower,” she said in a message sent via LinkedIn.
“I will always remember that trip and his kindness.”
He also loved music; rock ‘n’ roll was his favorite, particularly The Rolling Stones and The Beatles, so of course seeing Cirque du Soleil’s “The Beatles Love” show in Las Vegas one time was not enough.
Cathy said they went to see it three times.
She also recalled another time at an AGS Conclave in Phoenix when intellectual curiosity got her, Pete, and Jason in a bit of trouble.
As Cathy tells it, she wanted to go see the Frank Lloyd Wright house outside of Phoenix, Taliesin West. She convinced Peter and Jason they could slip away to see it and still make it back in time for the President’s Party that night.
All three of them were enthralled and decided they needed to stay to watch the sunset, then watch a video about the house, and then meet the people who run it.
By the time they got back to Conclave, the party was almost over but they had a plan—they were all going to enter the party through different doors and then appear at opposite ends of the dance floor like they had been there all along.
As it turned out, they were missed by then AGS President and CEO Ruth Batson, who was giving them all the stink eye on the dancefloor.
“We’re like fools, coming in the side doors, dancing like nobody would miss us,” Cathy said.
Brilliant as he was, Pete was not without a sense of humor.
Mark Clodius of Clodius & Co. Jewelers in Rockford, Illinois, shared this story with me via email.
“Monika [Clodius] and I attended a diamond-cut lecture at JCK in the early 2000s. We had just opened our store, and we were not known inside the trade at all. Peter gave a number of very interesting and thought-provoking points about diamond cut/proportions and finish.
“He asked for questions at the end of the lecture and I had one. He called on my raised hand, and I asked my question. He initiated his reply with ‘as clear as the hair on your head’ and stopped, as audience members laughed because I am bald! He went on with his answer and came over to us afterward and apologized and we chatted a bit.”
While they were chatting, other people, including Gary Roskin, Richard von Sternberg, and David Federman, joined them and the group went out to lunch together.
Lifelong friendships were made that day, and Clodius & Co. Jewelers ended up joining AGS and developed a successful business.
“Peter always had a smile and time for us every time we met over the years,” Mark wrote. “He will be missed.”
Pete is survived by four brothers, Steve, John, Paul, and Phil; two daughters, Melissa (son-in-law Chad) and Elise; and seven grandchildren: Tyler, Kendall, Brayden, Kaleb, Logan, Ryder, and Julia.
Rest well, Pete, and thanks for everything.
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