Prof. Dr. Henry A. Hänni: On a life in gemmology, curiosity, and the courage to question

Show notes

This episode was originally recorded in Swiss German in the summer of 2024. The English version you hear is a voice-over, with Laurent Cartier reading his own words and Martin Herzog voicing Henry, so the conversation could reach a wider audience.

In this episode of Hidden Gems, Laurent Cartier sits down with Professor Dr. Henry Hänni in the summer of 2024 for a wide-ranging conversation about a life spent with gemstones. Henry passed away on 8 January 2025, and this episode is shared in his memory — and as a tribute to a teacher whose curiosity, scientific rigour, and humour shaped a generation of gemmologists, Laurent among them.

Henry traces his unconventional path into science: a fascination with colour and symmetry from childhood that drew him equally to plants and stones, an early job as a workshop assistant at the University of Basel's mineralogical institute, and a self-directed return to high school via correspondence and evening classes that allowed him to graduate at 24 and begin his university studies. He recalls discovering that fieldwork was not for him, finding his place in the laboratory, and joining SSEF — then in Zurich — under its first director, George Bosshart.

The conversation moves through the work that helped define modern gemmology: the development of instrument-based analysis using X-ray microprobe, X-ray fluorescence, FTIR and Raman spectroscopy at a time when most gemmologists relied on the loupe and the microscope alone; the seminal 1990 Journal of Gemmology paper on Kashmir sapphires that pushed the trade toward evidence-based origin determination; and the work on Colombian emeralds that revealed artificial resin treatments being passed off as oil — research that produced a meeting in Bogotá Henry ultimately could not attend, having received death threats.

Henry reflects on the work he is most proud of — his explanation of how cultured pearls form, published in German, English and Chinese — his investigations into pearl formation that involved cutting natural pearls in half to understand what was inside, his correction of the misnamed "chloromelanite" to maw-sit-sit with Jürg Meier, and his discovery of heat treatment in demantoid garnets, which he was the first to describe. He and Laurent discuss the growing gap between specialists and generalists in gemmology, the importance of teaching, and Henry's lifelong impatience with what he politely calls "talking nonsense" — the small false claims that, left unchecked, fly everywhere.

The conversation closes with Laurent telling Henry that SSEF has established the Henry A. Hänni Scholarship, which supports students from gemstone-producing countries — a recognition Henry received with visible emotion.

About the guest Professor Dr. Henry Hänni (1945–2025) was Director of SSEF, the Swiss Gemmological Institute, from 1990 to 2009, and Professor of Gemmology at the University of Basel. He trained as a geologist and mineralogist at the University of Basel, where he completed his PhD before joining SSEF as a researcher under George Bosshart. Over a career spanning more than four decades, Henry authored landmark studies on Kashmir sapphires, emerald treatments, cultured pearl formation, new analytical methods, origin determination and many other subjects, and helped establish the scientific foundations of modern gemmological practice. He was a mentor to generations of gemmologists worldwide.

Henry's research publications: Explore here

The Henry A. Hänni Scholarship Established by SSEF in Henry's honour, the scholarship supports students from gemstone-producing countries to pursue gemmological education at SSEF, covering tuition, travel, and accommodation. More details here.

**Credits **Hosted by Laurent Cartier (SSEF). Produced by Martin Herzog, who also voices Henry Hänni in this episode. Intro music composed by MMYYLO. A podcast by SSEF — the Swiss Gemmological Institute.

Transcript

Henry Hänni: I think it's really my fascination for gemstones themselves that led me to gemology, the beauty of colour and symmetry. It's a bit like flowers. Gemstones are colourful. They're symmetrical as crystals. That's what got me hooked.

Show Opener: SSCF presents the Hidden Gem podcast, conversations with the world's leading people behind the journey of gems and jewels from the source to the finished piece.

Laurent Cartier: Today on Hidden Gems, I'm sharing a conversation with Professor Dr. Henri Hänni, Director of SSAF from 1990 to 2009, whose work helped shape modern gemology. We recorded this interview in the summer of 2024. Henry passed away on January 8th, 2025, and it's a true privilege to be able to share his voice, his humour, and his clarity with you now. Henri's path into gemology was anything but conventional. From workshop assistant at a mineralogical institute to a doctorate in geology, and then to becoming director of SSEF, where he advanced gemology with scientific rigour without ever losing sight of wonder.

Laurent: Henry, how did you even get started with stones—with gemstones? How did you get into that?

Henry: I’ve been fascinated by the striking beauty of colour and symmetry ever since I was a little kid. That fascination led me toward plants—specifically flowers—and also stones. After a long journey, which included partially attending high school and a few other things, I came to a crossroads where I had to decide what I was going to do next. My father asked, “So, what do you want to do now?” and I said, “Either something with plants, or something with stones.” Then he took me to the botanical institute, but they said, “We only take girls.” Over at the mineralogical institute, they said, “Yes, we could use someone in the workshop.” So that’s where I started, as a workshop assistant. And of course, I immediately got to know all the students there, and I really liked their lifestyle. I wanted to be one of them, so I set out to get my high school diploma—took correspondence courses and evening classes. I ended up graduating high school at 24, which allowed me to start studying. It was definitely an unusual path.

Laurent: So you started out fueled by your passion, and later you went to university so you could put that passion into practice professionally?

Henry: Exactly. And I worked the whole time while I was studying, so it was like carrying a double load. But it all worked out fine.

Laurent: You had the drive to go into gemmology, right?

Henry: A strong drive, yes.

Laurent: Who shared that interest in stones and plants with you—your father or your mother? Henry: Neither, actually. My dad was a medical lab technician who operated on mice and rats. Not exactly the same field.

Laurent: But there was still some sort of scientific mindset going on—an ability to observe closely, perhaps? Henry: During those four years of high school, I had a really good biology teacher. And when you have a really good teacher, you end up thanking them for the rest of your life.

Laurent: Then you went on to study at the University of Basel, correct?

Henry: Yes, I studied in Basel, and at the same time, I kept working as a workshop assistant right up until I finished my PhD. After that, I went looking for a position that offered better pay and where my doctorate would be recognized. There was an opening at SSEF—back then, it was still in Zurich—and I went to introduce myself. George Bosshart said, “We could use someone like him,” so he hired me.

Laurent: But before you actually started at SSEF, you did a lot of traveling—Greenland, for example—doing geological fieldwork and mapping. Were you already interested in gemstones at that time, or did that come later?

Henry: I quickly realized that field geology wasn’t really my thing. I didn’t enjoy all the heavy hiking. I was more into lab geology or mineralogy. And gemology is basically a lab-based discipline—you’re not trudging around outside all day.

Laurent: And gemmology is often seen as a “soft science.” I’m sure you felt that attitude at the university, where some folks didn’t take it too seriously. How did you handle that?

Henry: Back then, gemology had only a few pioneers or role models—Eduard Gübelin was one of them. I watched what he was doing and noticed what else was possible, so I went ahead and did it. That mainly led me to expand instrument-based gemology—using X-ray microprobe, X-ray fluorescence, FTIR, Raman, and that kind of equipment.

Laurent: So you basically played a big part in making gemmology a proper science—really pushing it in a scientific direction. Because hardly anyone was using advanced analytical methods for gemstones back then. It was mostly microscopes and loupes—even for Gübelin. That’s your big contribution to gemology, isn’t it?

Henry: I still prefer someone using a loupe over not looking at all—at least they’re looking. Or maybe opening one eye and closing the other with the loupe, right? (laughs) But yes, the microscope is better, and it’s standard today. It’s more comfortable; you can rest your arms so the image doesn’t shake, which is great. It also lets you “freeze” what you’re seeing—take slides or photos—and print them. Gübelin’s photo atlas, for example, is like a bible you can flip through and is a great reference for gemologists.

Laurent: But you weren’t just in the lab all the time. You mentioned lab gemology, but you had a good friend and did a bunch of trips to gemstone-producing regions…

Henry: India, Pakistan—very important. And Burma, too.

Laurent: Was there a particular trip that stands out for you?

Henry: Not really—I just always looked forward to the next one. I really liked being in Australia, and I went to see a diamond mine in China.

Laurent: How was that?

Henry: Honestly, it was kind of monotonous. They weren’t really mining anymore—apparently, they’d run out of diamonds. The hole was still there, and people were still poking around desperately, but there was nothing left. I also saw the Big Hole in South Africa.

Laurent: After all those trips and all the people you met, why do you think people search for gemstones? What’s behind that fascination?

Henry: Personally, I was looking for gemstones to take them home with me as reliable reference samples for later scientific studies—to see, for example, how much vanadium is in a Sandawana emerald, and so on. That ended up becoming a huge collection, which luckily is now at the SSEF.

Laurent: But you also met many people for whom it wasn’t just about science, right?

Henry: I think it’s really my fascination for gemstones themselves that led me to gemmology—the beauty of colour and symmetry. It’s a bit like flowers: gemstones are colourful, they’re symmetrical as crystals, and later on, if they’ve been tumbled, they get cut like crystals, too. I think that’s something intrinsic.

Laurent: So part of your curiosity was just wanting to understand colour, crystallinity, how they grow, how you can tell them apart…

Henry: To really understand it, I probably would have had to study physics—like, why exactly is a sapphire blue, or why does a tourmaline turn out brown, for instance. But in practice, it’s mostly about identifying what you’re faced with and whether or not it’s been treated. Those were the main questions. You have to stay sharp and have a good memory to understand what you see.

Laurent: You also brought other strengths with you when you got into this industry. You cut stones yourself, prepared them yourself—so maybe you had a more hands-on approach than people who only look at the science. Did that push you to keep experimenting?

Henry: Yeah, it’s basically a trait of mine—I always feel the need to question things. If someone says something I don’t think is true, I’ll check it out on my own. One example is how, for years—decades, really—people said that a grain of sand slipping into an oyster is what forms a pearl. But I just couldn’t imagine that a creature living in the sand and in the water would be bothered by a grain of sand. And how would the sand even get so deep into the flesh, where the pearl is eventually found? That kind of puzzle is what drove me forward.

Laurent: So, how exactly does a pearl form, then? What did you find out? Are we any smarter about it now? Do you know the answer?

Henry: Well, are we smarter now? I did some experiments involving injuries to the edge of the shell to see how they heal. My view is still that when the outer mantle gets injured, some of its cells get carried deeper inside, where they form kinds of cysts. The interesting part is that the edge of an oyster shell isn’t always the same throughout its life—when the oyster is young, the edge is in a different position than when it’s older. Over time, the oyster’s shell edge keeps growing outward. Early on, it produces calcite, and later aragonite, which is why most natural pearls have a brownish core at the centre and then only later develop their proper lustre around the outside. That’s why you’ll sometimes hear people talk about “immature pearls.” If they’re harvested too soon and they’re still brown, nobody really wants them, so they get thrown out. Once they turn white and nacreous, then they’re acceptable.

Laurent: You really wanted to get to the bottom of this—so much so that you had the courage to cut pearls in half, even natural pearls, just to see what’s inside.

Henry: Yes, and that had its price. It meant sacrificing a few natural pearls, but then at least we knew for sure. It was also important to publish those findings—to really spread the word so other people could benefit from that knowledge.

Laurent: Out of all your research projects and publications, are there one or two that you’re especially proud of?

Henry: My explanation of how cultured pearls form—that was published in German, in English, and also in Chinese. I’m proud of that one.

Laurent: There’s another one I think a lot of people know about: your work on Kashmir sapphires. In 1990, you published a paper in the Journal of Gemmology—it was one of the first truly scientific studies on that subject. What motivated you? Why was that topic so important?

Henry: Well, I noticed that some dealers were basically mislabelling stones, putting on a product label that wasn’t accurate—

Laurent: You mean, misrepresenting the origin?

Henry: Yeah, basically. There’s a difference between Kashmir sapphire and Sri Lankan sapphire. Back then, those were two main competing origins found on the market. You can tackle the problem from different angles—chemistry, spectroscopy, microscopy. Those were the tools we had at the time. We even used electron microscopy in some cases. If we were lucky enough to polish the stone down to an inclusion, we could see what it really was. Eventually, that built a database of what’s probably from Kashmir and what probably isn’t.

Laurent: And why is that label—Kashmir versus Sri Lanka—so important?

Henry: Because the price difference can be a factor of ten.

Laurent: And so they need gemologists to confirm that origin.

Henry: Yes. And that’s about the time gemologists who didn’t really know how to do it would just declare something to be Kashmir if they thought it might be, without actually having much evidence—just going by looks. I wanted to sort of, well, cut down on that kind of approach.

Laurent: That probably didn’t make you popular with some dealers or even some gemmologists. How did the trade react to your insistence on being so transparent and scientific?

Henry: My goal was to show others what to look for so they’d have a chance to identify a true Kashmir sapphire. That became the publication with all those beautiful images, including rock samples from Kashmir that had sapphire crystals which we could also analyse for trace elements. It’s all in the collection here—Pascal Entremont, I believe, also provided us with some of these samples.

Laurent: But you never actually visited the Kashmir mines yourself, right? They’re over 5,000 meters above sea level—really tough to get to.

Henry: No, I never did.

Laurent: You also had some run-ins with Colombians over artificial resin versus oil treatments. Could you tell us a bit about that?

Laurent: Yes, that’s when dealers started feeling overwhelmed and asked labs for help, because more and more emeralds were being treated. Before that, they didn’t really mind—they’d just say the stones were “oiled.” But with today’s instruments, we can see exactly what kind of oil it is. I realized that in many cases, it wasn’t actually oil—it was some type of artificial resin. I found a way to differentiate between oil and artificial resin. You can clean the oil out, but artificial resin is much harder to remove. Once I started pointing that out, there was a big meeting in Bogotá.

Laurent: You couldn’t go, right? I heard you even got death threats—people didn’t want you to show up in Bogotá and present your findings.

Henry: I’d better not confirm that; otherwise, they might come for me again! (laughs) Actually, a funny anecdote from Colombia: People there had such high regard for the GIA—“GIA, GIA, GIA,” as if it was the best and only real scientific institution. At an international emerald conference, an American woman from the GIA lab was presenting, and she showed a photo of her microscopic setup with a camera on top. Laurent: Mhm…

Henry: She pointed at the camera and said, “This is our laser.” But it wasn’t a laser. There wasn’t a laser to be seen anywhere! That’s when it dawned on me—sometimes the reputation is way bigger than what’s actually going on behind the scenes. I just hope that never becomes the case for the SSEF, and so far, it seems it isn’t.

Laurent: So did you speak up in Colombia and say, “That’s not a laser”?

Henry: No, you can’t really do that…

Laurent: You can’t, yeah. Though sometimes you did speak up, right? You’ve been known to voice your opinion.

Henry: Yeah, well, regarding those death threats in Bogotá… I remember riding in a car next to that American woman. When I got in, I let her have the window seat. She asked, “Don’t you want to sit here?” and I said, “No, no,” and once she was seated, I told her, “You know, they do a lot of shooting around here.” (laughs)

Laurent: But she made it out just fine?

Henry: She made it out in one piece, yes. Just joking around.

Laurent: Colombia was big money, especially back then, with emeralds—it was a different era, and it could’ve been dangerous for you.

Laurent: These days, gemmology is getting more and more scientific. We have extremely advanced methods, and some people don’t even bother with the microscope anymore; they don’t look at inclusions themselves. What’s your take on that, and what advice would you give young gemologists?

Henry: Well, there’s a growing gap between specialists and generalists.

Laurent: You were a generalist?

Henry: I was a generalist who became a specialist, and I’d suggest every specialist go back at some point and see how things look from the basic level—what people are actually doing, what they’re talking about. You can’t really force people to do that, but it helps.

Laurent: So, we’ve got some stones here—jasper, charoite from Siberia, Russia. What are you going to do with them? Are you going to cut them?

Henry: I’ll give them a nice shape and then polish them so they become cabochons. My hope is that gemmologists who look at them won’t just test refractive indices or density, but instead say, “Oh, that looks like charoite, it could be charoite.” Over the years, way too much time has been spent using refractometers and polariscopes to identify faceted gems. During Covid, gemmologists couldn’t meet up in person, and I thought, “We can’t just let a year or two go by without doing anything. Let’s keep gemmology moving!” So I put together a set of stones that you can tentatively identify by sight, like tiger’s eye—just to refresh the memory of names, or jadeite, nephrite, etc.

Laurent: That’s really the foundation of gemmology: being able to recognize and identify. In the lab, we mostly handle rubies, sapphires, and emeralds of high-quality. But mineralogy and gemmology are actually way broader. There are hundreds of different stones you can use. You’ve got a special ring you’ve had for a long time with maw-sit-sit in it. Can you tell us a bit about that stone? Have you visited the mine or the village in Burma?

Henry: Not the exact village, but I have been to Burma a few times.

Laurent: What’s so special about maw-sit-sit?

Henry: It was another instance where something didn’t sound right to me, and it spurred me to investigate. At the time, Eduard Gübelin was the top gemologist in Switzerland, and he presented that material—he showed it off at meetings of the SGG (Swiss Gemmological Society). Then I got hold of a sample and studied it with Jürg Meier. We found that the name he gave it—“chloromelanite”—couldn’t be correct, because chloromelanite is already a term for a certain pyroxene solid solution mixed crystal. So we prepared a thin section to see what it really was. Turns out it contains jadeite, albite, kosmochlor. Maw-sit-sit is a nice gem material.

Laurent: That’s one of the beautiful things about gemstones, right? You’ve probably seen a lot of it in your 60-year career. Sometimes you get a discovery site that might only produce for a year or two, or maybe ten years or a hundred, and then it’s gone.

Henry: Exactly—it’s crazy. Somebody could be eager to buy a certain stone, but suddenly it’s unavailable. Nobody has it, nobody asks for it, or maybe the mine’s empty.

Laurent: What are some examples of that? You were one of the first people to analyze Winza rubies (from Tanzania) and have a chance to study them scientifically, right?

Henry: Yes, that was just one of many new finds. And the main question there was origin determination—how to tell them apart from rubies of other origins.

Laurent: I guess you’ve dealt with the fact that sometimes the trade struggles to understand why origin determination can be so difficult. There can be disagreements between labs because nature is complex; there’s overlap. Is that how you see it?

Henry: Yes, and in addition, people don’t always want to accept a result that goes against their preconceived notion. They might have paid for a Burma ruby, so it must be from Burma—end of story!

Laurent: So you had to deliver bad news sometimes?

Henry: I’m glad I’m out of some of those challenging and tense situations now. It’s not fun. I even got a death threat once—actually, yeah, a death threat. Right here in Basel, a woman came by and said, “I’m sending my husband over,” and I checked his name and saw that in Belgium he’d already killed someone. She wanted her ruby to be considered Burmese.

Laurent: And what was her ruby, actually?

Henry: Not Burmese. It was heated, something else.

Laurent: And you took that death threat seriously?

Henry: Of course, immediately. I went to the police, and they made a note of it.

Laurent: And here you still are!

Henry: Yes, but you do start looking over your shoulder at every street corner when something like that happens. (laughs)

Laurent: Let me ask: do you have a favourite gemstone? You’ve seen so many—hundreds of thousands of stones in your life and career. Is there one that really stands out?

Henry: I love garnets, because they come in various colours, they form mixed crystals, and they’re easier to grasp scientifically. Take the pyralspite series, for instance—you can see how the colours result from variations in chemistry. I just think garnets are amazing.

Laurent: Which kinds? Demantoid, tsavorite—everything?

Henry: All of them, yeah. Demantoid, for example—one day, a good friend brought me a demantoid to look at, and I realized it had been heat-treated. I’d never seen a heat-treated demantoid before. Byssolite needles—actually a type of hornblende containing water—if you heat them enough, the water escapes and creates stress cracks. It’s mind-blowing. The first time I brought that up, nobody had written about it anywhere.

Laurent: So you’re the first one who described heat treatment of demantoid. That wasn’t really known, even though they were apparently doing it in Russia. Maybe still do.

Henry: Yeah, and if you’re just looking through a loupe in some random orientation, you might not notice those internal features or interpret them correctly.

Laurent: Why do they heat-treat demantoid, but not other garnets? What’s the point?

Henry: You can tweak the ratio of Fe2+ to Fe3+, which affects the colour.

Laurent: So you get a better colour out of it. And you’ve seen colourless garnets too, right? That’s what’s so fascinating about garnet—it can come in every colour.

Henry: Colourless is just a grossular garnet with nothing in it. And that’s what fascinates me—it’s explainable, too.

Laurent: It’s real detective work: you see the colour, then you can dive into the science behind it. Henry: Do you have a favourite stone?

Laurent: I do. I love spinel, emerald, and pearls. That’s something we share—I did my PhD work on pearls because you were so passionate about them and introduced me to so many contacts. I discovered a whole new world of pearls. So what is it about pearls for you? They’re not geologically formed. Did it really start with that notion about a grain of sand and you just didn’t believe it, so you had to dig deeper? Henry: Yes, and also because they started showing up in the lab. In the beginning, SSEF only graded diamonds, then diamonds and coloured stones, and eventually pearls arrived.

Laurent: Right, SSEF was founded in 1972 as a foundation. George Bosshart was the first director, and then you became the second. How did SSEF grow so big over the past 50 years? You played a huge part in that. Henry: I should probably explain why it didn’t grow at first: there was a foundation board made up of jewelers who could directly influence the lab in Zurich. Things changed when we moved away from that environment (to Basel), and the board got a new composition, which gave us more space, physically and otherwise. Initially, they didn’t want us traveling, so I paid for some trips to trade shows out of my own pocket because I felt it was necessary. Later, when I became director, SSEF covered those costs. Over time, the board’s understanding grew.

Laurent: And you always insisted on the highest scientific standards. You never settled for the status quo—you wanted more data, more knowledge, more understanding. That was a big factor, too.

Henry: Yeah, that kind of outlook can really give you options.

Henry: And you were never lazy as a scientist—you, Henry Hänni, always kept pushing. Henry: That what’s fun!

Laurent: That’s what inspires so many people who’ve worked with you—just staying curious. And you’re still curious today about new stones, new localities. There’s plenty more to discover, right? How do you see the future of gemology?

Henry: Hard to say. I think there’ll be an even bigger gap between specialists and generalists. Laurent: You’ve met all sorts of folks—collectors, buyers. Some are in it for the money, but others do it purely for the love of gems.

Henry: That’s a mystery to me. I’m not so familiar with the buyer’s side because there’s always the filter of the jeweler or the stone dealer in between. I really don’t know the end consumers personally.

Laurent: Another thing: a lot of people know you as Dr. Hänni or Professor Hänni. You’ve lectured all over the world, published in every gem journal.

Henry: I think it’s great that you bring it up, but…

Laurent: I do, because there are so many people in the trade and the gem community worldwide who know your name. I was in the US recently, and when I mentioned SSEF, several people asked me, “How’s Henry Hänni doing?” Your name is still widely recognized. What don’t people know about you?

Henry: Probably that I’ve been divorced twice, for instance—that my work often took priority over family. And yet my daughter still loves me, which is wonderful. She’s a great daughter.

Henry: She helps me out now that I have a harder time walking, seeing and hearing.

Laurent: Thinking about the next generation or the one after that, do you think there’s still more to discover? Henry: Oh yes, absolutely. But it’s like adding a drop of blue ink to a whole tank of water—how much does it take before you see colour appearing? Even if my two grandkids are smart and wonderful, there are still so many people out there who’d rather peddle nonsense. So we need to stay curious and scientific. Laurent: Another point: when you started out, it was a pre-digital era. Now everyone’s online with smartphones—even in the remotest villages in Burma, people have internet on their phones to show off stones they claim are worth a fortune. How different was it 50 years ago, with no computers or real phone lines?

Henry: How was it at first? Telephone…

Laurent: Telephone, yeah—or in places like Madagascar or Burma, there probably weren’t phones at all. So you just had to go there yourself.

Henry: Yes, and I did.

Laurent: You’ve been pretty much everywhere, right? Almost every country.

Henry: Not everywhere. I’ve never been to West Africa, but I have been to South Africa and East Africa. Laurent: I’ve got good news for you, Henry. We’ve decided to set up a new scholarship at SSEF called the “Henry A. Hänni Scholarship.” The requirements are that the student must come from a gemstone-producing country. We’ll pay for the course, flight, and hotel.

Henry: No, come on!

Laurent: Yes, really. It’s going to be called the “Henry A. Hänni Scholarship.” Part of the inspiration came from what we’ve been discussing.

Henry: That’s almost too great an honour.

Laurent: You’ve shown tremendous curiosity about these countries, forged lots of wonderful contacts, and there’s another topic we haven’t covered as much: you’ve done so much teaching, always sharing your knowledge with me, with everyone—from Mogok to people all over the world.

Henry: I’m glad we can talk about it like this, because Michael never brought that up—he always had to ensure I didn’t cast a shadow over him. And now, apparently, that’s in the past. How do you deal with this stuff? I might not have a lot of time left, so this news makes me really happy.

Laurent: And why has teaching been so important to you? Some people keep their knowledge to themselves.

Henry: Because it bothers me when people talk nonsense. You know, “when the shit hits the fan”

Laurent: Then what happens?

Henry: Then it flies everywhere. If someone starts saying pearls form around a grain of sand, you have to clean up this nonsense one bit at a time. I wanted to prevent that. And I wanted to show that people can understand these concepts if they attend a course, see what we’re talking about, refresh their high-school chemistry or physics, and pass on to their grandkids that, hey, this stuff matters.

Laurent: So you’d say you’re only a good scientist if you can explain a theory to kids?

Henry: I’ve tried to do that.

Laurent: And you did it really well.

Laurent: So, for example, how does an emerald form? There’s chromium, there’s beryl—how does that happen?

Henry: In Pakistan, I once stood on the boundary between a pegmatite and an ultrabasic rock. In a reaction zone maybe 15 to 20 centimetres wide, there are emeralds. It’s incredible to see this firsthand. The ultrabasic rock released a bit of chromium, which migrated into the pegmatite, where there was already lithium and beryllium.

Laurent: That’s what makes emeralds so rare—there aren’t that many places where that particular combination occurs.

Henry: Yes, although as the years go by, we discover more. When I started out, ruby was far rarer than it is now. I’d say 30 or 40 new ruby sources have opened up since then.

Laurent: And these days, you’re enjoying cutting cabochons, just having fun with stones? Henry: Absolutely—I love it.

Laurent: Do you think your unconventional path—starting as a workshop assistant at the mineralogical institute, preparing samples—rather than going the direct academic route, helped you keep things communicate scientific principles in simple ways for people?

Henry: I think it’s just a knack, being able to explain things in a certain way.

Laurent: But have you always had that knack, or did you work at it?

Henry: No idea, to be honest. Were you in my lectures?

Laurent: Yes, I attended your lectures at the university around 2003–2004.

Henry: Were they good lectures?

Laurent: They sure were—that’s how I got interested in gemology! I was studying geology and wasn’t entirely sure, then I saw your gemmology class with all your travel photos and stories. It was both scientific and very human—you showed pictures of pearl farms in Tahiti, of Mogok, Colombia, Sri Lanka…

Henry: Flash, flash, flash…

Laurent: Yes, I realised gemology was a nice blend of science and travel and meeting people. Gems are really a microcosm of the world. Analysing diamonds—or any stone—can help you understand how the earth was formed, and at the same time there’s so much more to it. With pearls, I was amazed at the idea of finding DNA in them, dating them, looking at corals—there’s always more to discover if you collaborate with specialists from other fields. And it all started when I attended your lectures. I saw it wasn’t just abstract—it’s got its own logic, and it’s exciting, colourful. So thank you for that, Henry. Thanks so much for this conversation, Henry.

Henry: Thank you for the interview and for the good news.

Laurent: Here are your stones back—take them home and keep up the good cutting, Henry!

Laurent: Our guest was Professor Dr. Henri Hänni, a pioneering gemologist and a mentor to many in the field, myself included. That was another Hidden Gem by SSEF, the Swiss Gemological Institute. Thank you for listening.