George Peter “Pete” Yantzer
November 10, 1948 – January 10, 2026
George Peter “Pete” Yantzer, a respected gemologist and influential figure in modern diamond grading, passed away this past week following a battle with cancer. He was 77 years old.
Pete’s career in gemology spanned several decades and left a lasting mark on laboratory standards and industry thinking—particularly in how diamond cut quality is understood, measured, and communicated.
A graduate of the Gemological Institute of America in western Los Angeles in 1972, following his service in the U.S. Air Force, Pete began his career at GIA as a staff gemologist and instructor. He went on to work in both the New York and California offices.
In 1976, as GIA expanded its laboratory and educational facilities, Pete was appointed director of GIA’s Los Angeles Gem Trade Laboratory, opening a small operation with a staff of three, including himself. During his tenure, the laboratory grew dramatically, driven in large part by the early stages of what became known as the diamond “investment” boom—a period when investment firms were marketing large volumes of GIA-graded diamonds, requiring the rapid addition of diamond graders and expanded laboratory capacity. Pete’s leadership helped push the lab through this period of intense growth.
In 1979, Pete stepped away from GIA to pursue other interests. But within a short time, he was asked to return to GIA, this time to Santa Monica to help direct the Gem Trade Laboratory there as it was to operate a double shift during the height of grading demand. As the diamond investment boom began to slow, this expanded operation was no longer needed, and Pete ultimately left GIA, bringing his years with the Institute to a close.
He returned to the trade in 1996 as director of the newly established American Gem Society Laboratories, headquartered in Las Vegas. Over the next twenty years, Pete helped transform AGS Laboratories into a top-tier diamond grading institution. He led research and development efforts and was instrumental in creating the AGS diamond Cut grading system—a methodology designed to evaluate light performance. Developed over several years of analysis and testing, the system significantly influenced cutting standards throughout the industry and elevated the role of Cut quality in determining beauty and value.
In 2005, Pete received the Robert M. Shipley Award, the American Gem Society’s highest recognition, honoring his service, leadership, and contribution to gemological knowledge.
Pete stepped away from his role at AGS Laboratories in 2015, continuing as a consultant for several years. In 2016, he was honored with the first Lifetime Service Award from the Jewelers 24 Karat Club of Southern California, recognizing his decades of professional contribution and leadership.
Throughout his career, Pete was known not only for his diamond grading and technical insight, but also for his willingness to question the gemological routine. He spoke openly about grading consistency, laboratory standards, the impact of synthetics, and whether existing color and clarity scales truly reflected what consumers could see or value. His views—shared in industry forums and interviews with publications including JCK Magazine and National Jeweler Magazine—were thoughtful, practical, and often ahead of their time.
Colleagues remember Pete as a great guy, a careful grader, and a professional who believed that a better-cut diamond is simply a better-looking diamond.
“Peter Yantzer didn’t just change diamond grading—he shaped the people who practice it,” said Katherine Bodoh, CEO of the American Gem Society. “His decades of leadership, curiosity, and generosity helped elevate an entire profession. We will forever be grateful for his impact on AGS and the industry, and we will miss his warmth, wit, and deep love of gemology.” — Katherine Bodoh, CEO, American Gem Society
“Although I have known Pete for a long time, I had the privilege of working briefly with Pete Yantzer during his tenure as director of the AGSL (American Gem Society Laboratory). Throughout that time, he was fun to be around, always joking, yet with a sincere, heartfelt desire to help our industry. Pete was fervent about the idea that “cut grading is the most important factor in diamond beauty,” a principle that shaped the American Gem Society laboratory from its inception. Under his focused guidance, AGSL became a pioneer, introducing the first cut-assessment standards using non-contact devices, consistent with AGS’s rigorous approach. For nine years, AGSL had provided the trade with proportion-based cut grades, but things truly changed in 2005, when Pete introduced the Angular Spectrum Evaluation Tool (ASET®) to the trade. With ASET, AGSL moved beyond the old, subjective grading methods and adopted a new, scientific system that quantifies how a diamond interacts with light. Pete was excited about the changes he was bringing. It was a turning point in the history of cut grading, and it all happened under Pete’s watch. I am truly honored to have known him and call him my friend. I will dearly miss him.” — Al Gilbertson, CG, Project Manager, Cut Research (Carlsbad) GIA
“Pete frequently expressed admiration and heartfelt gratitude towards his closest mentors and teachers who included industry legends like Richard T. Liddicoat and Bob Crowningshield. For those of us who had the privilege of learning from and being mentored by Pete, we feel the same towards him.” Said Jason Quick, Sr. Director of Cut Grade Research at GIA. “Beyond Pete’s pioneering gemological contributions, it will be his contagious smile, caring heart and brilliant inner light which will continue shining on in the memories of those of us fortunate enough to know him.” – Jason Quick, Sr. Director, Diamond Cut Research at GIA
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Pete is survived by his four brothers—Steve, John, Paul, and Phil—daughters Melissa (and her husband, Chad) and Elise, and grandchildren Tyler, Kendall, Brayden, Kaleb, Logan, Ryder, and Julia.
Further details regarding services and remembrances will be shared when available.
