Exit Interview With GIA Legend Tom Moses

Pick up any sapphire ring at a jewelry counter, ask about the stone, and there's a good chance the salesperson hands you a folded card stock report with GIA printed at the top. Most shoppers glance at the grade and move on. Tom Moses spent nearly 50 years ensuring that number actually means something.

Moses, GIA's executive vice president and chief research and laboratory officer, announced his departure in March 2026 and will leave in May after joining the institute's Santa Monica laboratory in 1976 as a freshly credentialed Graduate Gemologist. By the time JCK published his exit interview, he had overseen more graded gemstones than perhaps any single person in the history of the trade, including a personal encounter with the Hope Diamond. GIA has confirmed there are no plans to directly replace him; his responsibilities will be divided among several roles. That structural decision says something about the breadth of what Moses actually did.

Why a Standardized Grade Is Worth More Than It Looks

The four Cs on a diamond report, or the treatment disclosures on a colored stone report, are not descriptions written by the jeweler selling you the piece. They are the output of a methodology refined over decades, calibrated to be consistent across GIA's global laboratories. That consistency is the entire point. When you buy a ruby in New York versus Bangkok, a GIA report means the same thing in both cities because the same standards, processes, and technologies are applied at every location.

For everyday buyers, this matters most when color and clarity expectations need to be predictable. A grade issued today should match what a subsequent appraisal or resale report would say years from now. Moses spent much of his career building the infrastructure, including AI-assisted clarity grading developed in partnership with IBM, to tighten that consistency. As he explained in one earlier JCK conversation, clarity grading remained "the last frontier" of automation precisely because it requires assessing size, number, nature, and type of multiple characteristics simultaneously. That complexity is why a GIA report carries more interpretive weight than a simpler certification from a less rigorous lab.

The Lab-Grown Question Every Buyer Should Ask

One of the most consequential questions Moses addressed in his exit interview is whether a lab-grown diamond could ever become commercially undetectable from a natural one. His answer was unambiguous: "I don't think there will be an undetectable one that can be commercially grown." The reason is physical. Growing a diamond quickly enough for commercial production requires different temperatures and pressures than those found in the earth's mantle, and that acceleration leaves fingerprints: differences in the outer shape of the rough, in growth patterns and defects, and in subtle chemistry. "In the earth, it can take 100 or 1,000 years to grow a diamond," Moses said. "In a factory or laboratory, you need to accelerate the growth time."

For shoppers, this means GIA's detection capabilities are a genuine safeguard, not a marketing claim. The institute also developed the GIA Match iD instrument specifically to catch fraudulent lab-grown diamonds inscribed with real GIA report numbers to impersonate certified natural stones, a practice GIA encountered directly and reported to law enforcement. If a report number is on the girdle of a stone you're considering, that number can be verified instantly against GIA's secure database.

Reading a GIA Colored Stone Report in Real Life

A colored stone report from GIA covers considerably more than a grade. Here is what each section tells you and how much weight to give it:

• Natural vs. synthetic identification: The most fundamental finding. A GIA Identification Report confirms whether a stone is natural or laboratory-grown. This is non-negotiable to verify before purchase.

• Treatment disclosure: This is the section most shoppers undervalue. Heat treatment is standard in the ruby and sapphire trade and considered acceptable; oils and resins in emeralds require more scrutiny because they affect long-term care and durability. GIA's ongoing research continues to refine how treatment disclosures are classified, which means a report issued after new research protocols may describe the same treatment differently than one issued five years ago.

• Geographic origin (on Identification and Origin Reports): Available for sapphire, ruby, emerald, alexandrite, Paraíba tourmaline, demantoid, jade, opal, peridot, and red spinel. Origin adds premium value and provenance context, but it is an opinion, not a guarantee, and should be weighed alongside price.

• Color description: Listed in qualitative terms for colored stones rather than graded on a numerical scale. Pay attention to the specific hue, tone, and saturation language; "vivid" and "strong" carry meaningful price differences at auction and resale.

• Cut and measurements: Relevant primarily for resale and remounting purposes.

What to Ask a Jeweler Before Paying

Before handing over a card, run through these questions:

• Does this stone have a current GIA report, and can I verify the report number on GIA's website before purchase?
• Does the report disclose any treatments? If yes, what care does that treatment require?
• Is the stone natural or lab-grown? If lab-grown, is that price reflected accordingly?
• For colored stones: is the geographic origin listed, and how does that factor into the asking price?
• Has the stone been re-treated or re-cut since the report was issued?

Which Stones Actually Hold Up Daily

Moses' decades of gemological research inform a practical hierarchy for everyday wear. Sapphire and ruby, both varieties of corundum at Mohs 9, sit just below diamond in scratch resistance and are among the most durable choices for rings and bracelets worn through handwashing, cooking, and gym sessions. Certain heat-treated stones, including many commercial sapphires and rubies, are structurally stable and safe for daily rotation provided they are set securely.

Softer and more porous materials require more selective wear. Emerald, despite its prestige, typically contains fractures filled with oils or resins and should be removed before contact with ultrasonic cleaners, harsh detergents, or prolonged heat. Opal is sensitive to sudden temperature change and low humidity. Pearls, at Mohs 2.5 to 4.5, are among the most vulnerable to daily contact and should be the last piece put on and the first taken off.

GIA's lab research, currently underway, continues to examine how certain treatments affect long-term stone durability, with potential implications for how future reports disclose and categorize those treatments. Buyers of treated stones purchased today may find that updated scientific standards shift the language used to describe what they own.

The Institutional Shift Moses Leaves Behind

Moses is not entirely disappearing. GIA will name him Chief of Gemological Research, Emeritus, and he has signaled an intent to keep working. "It would be very difficult for me to go, as the expression goes, cold turkey," he told JCK. "I'm still super curious." But the structural reality is that no single successor will occupy his seat. The institution he helped build, including its automated grading systems, its fraud detection instruments, and its ongoing treatment research, is now robust enough to operate without a single chief architect.

For shoppers, that transition is quietly reassuring. The credibility of the report in your hand does not rest on one person. It rests on a methodology that Moses, in 50 years, helped make durable enough to outlast him.