Sapphire Art & Science

Hello to everyone. Hello everyone. Welcome to the School of Jewellery Arts. My name is Marie-Laure, I'm a gemologist, art historian and I am a professor and researcher here at the School of Jewellery Arts and I am delighted to welcome Laurent Massy, Dr. Laurent Massy, PhD in physics, gemologist and also photomicrographer. So today we will be with Ghislain Ockerman, our colleague, who will be with you inside the chat and we will talk about sapphire, a fascinating gemstone that we are very fond of and I'm sure you too. So let's start with probably the most popular engagement ring. I'm sure you know it. Do you recognize it? It's in fact the engagement ring that Prince Charles gave to Princess Diana in 1981 and she chose a ring set with a sapphire at Gahar. Gahar was the jewel to the kings in Sri Lankan sapphire of 12 carats and here you can see the drawing of the ring. Princess Diana was particularly fond of sapphires and we know many pictures of her wearing different kinds of pieces of jewelry set with sapphires and the ring was preciously preserved by her sons Harry and William and William gave this ring as an engagement ring to Kate Middleton in 2011 and it became again very popular. So it is said that this ring is probably the most imitated engagement ring but in fact it's a very classical ring. In English we call it cluster ring and it has been popular since the 18th century in fact. It's the introduction for our talk about sapphire art and science so with Laurent we will discuss several aspects of this marvellous gemstone. So first we will discover what is a sapphire scientifically speaking and then we will focus on the blue colour that is so important and we will travel with you around the world looking for sapphire deposits at last. Let's start. Laurent, what is a sapphire? Hello everyone, welcome to this presentation about sapphires and hello Marie-Laure, thank you for having me here. So actually sapphire is a blue variety of the mineral called corundum. When corundum is pure, it's colourless and it's made of only aluminium and oxygen atoms. Corundum has a very good hardness, 9 out of 10 on the most scale, 10 being the diamond. The corundum also has a very good toughness and stability. What is the difference between hardness and toughness? One is resistance to scratches and the other one is the resistance to break. Absolutely, and stability? Stability is the resistance to chemicals, to heat and we will talk about heat a little bit later. That's the reason why I asked you. Yes, good stability when it comes to heat. So corundum has different varieties and we can see some of them on this picture here. Not only blue sapphires but also rubies, the red variety of corundum, coloured by chromium. But you do also have green sapphires, yellow sapphires, orange sapphires, so many different colours and even different blues. We will see the difference of the blues in a few slides. Corundum is actually made of aluminium and oxygen but when it's coloured some corundums will have some trace elements inside the structure. For sapphire you have to have both iron and titanium to give the blue colour to the corundum. As you can see here, in replacement of aluminium atoms, you see the corundum structure here. The oxygen atoms in white, the blue balls are actually aluminium and you have iron and titanium. Once you have iron and titanium close together you have the blue colour. It's enough for a very small quantity. Yes, we call them trace elements. They give the colour to the corundum and they are very, very, very small amounts. You need a very small amount of those elements to have the blue colour. Regarding the blue colour, for sapphire cutting, of course, the main goal of the stonecutter is to enhance the blue colour. In sapphire it's quite challenging because very often the colour is not even inside the rough sapphire. Here we have a picture of a and you can see the colour zoning that is apparent even outside the stone. Even the best qualities of sapphires can show a strong colour zoning. This is the case in the spectacular brooch set with very large Kashmir sapphire. We will talk later about the Kashmir origin, we've talked about that. You can see the larger stone, the picture, you can see it from the side and we can notice the colour zoning inside the stone. So even the best qualities can show colour zoning. It's very challenging for the stonecutter. The goal is really to show an even colour, especially for the sapphire when it's seen from the top. As you can see, in fact, inside the roof usually the colour is concentrated on the periphery of the stone. On the right you can see this diagram with the uneven distribution of the colour and on the tray sometimes we find sapphires that are called top colour or bottom colour depending on the concentration of the colour. So it's very rare, in fact, to have perfectly even colour sapphires. Regarding the cutting style, very often you will notice on the tray that sapphires are very deep and quite bulged on the pavilion part. Very often also we can notice that we have enough centre cullet for the sapphire and in fact it's related to the location of colour inside the roof. Usually sapphires are cut on the production places, for example in Sri Lanka they have a long tradition of sapphire cutting. Also there is an important cutting centre for cullet stones that is Jaipur in India and today in fact the most important cutting centre for corundums, rubies and sapphires, is Bangkok. Very often the cutting styles have many facets and in fact the cutting style is mostly related to taste and culture. So when the stones arrive, especially in France, the French jewellers prefer different cutting styles and most of the stones are recut because in France symmetry is very important and also we prefer cutting styles with less facets. We call it style à la française, French style cutting, and you can see in the middle of the presentation we have a sapphire that has probably been recut. It's a diagram of a recut. The cutting style most popular for the sapphire and coloured stones usually is what we call a mixed cut. What is a mixed cut? It's a mix of brilliant cut on the crown, the upper part, so it's an arrangement of triangular and losange facets. It gives brightness to the stone and the pavilion is step cut. That means we have quadrangular facets and step cuts enhance the colour. So it's a perfect combination to enhance the beauty of sapphire and on the right we have a very exceptional stone with very even colour, mixed cut. There is a very interesting cutting style also used to enhance some phenomenon. Yes, besides faceted stone you might also have sapphires that have been cut as a cabochon. If the sapphires have a lot of inclusions inside, the very thin and long needles, the mineral rutile, you might have, and if the stone is cut perpendicular to the c-axis as we might see here on the picture, here you have the rough that Marie-Laure talked about a few minutes ago. If it's cut perpendicular to the c-axis and if the sapphire has a lot of those inclusions, then the stone will display on its surface a star. We call this effect, this optical effect, asterism. Like this amazing star sapphire, a huge and amazing gem, more than 563 carats, shown in the American Museum of History in New York. You can see on the picture of the star here with the legs, so you have the centre of the star and then you have one, two, three, four, five, six legs due to the inclusions within the sapphire. The very interesting thing about this amazing gem is that the star is not only on the top but also on the bottom. Double cabochon. Yes. I'm really fascinated by these inclusions, so beautiful in fact. You actually can see here all the very, very thin needles. If we zoom in, you feel that there are some very, very thin and long needles within the structure and as you see, they give the birth to this amazing phenomenon, the star. Very, very organized. The mineral kingdom is a very organized crystal. Absolutely. Why do we love so much sapphire? You told us that in fact, Columbum comes in almost all colours, but in fact, the two more sought-after stones are the ruby, the red variety, and the sapphire, the blue variety. In the Western world, in fact, blue is probably the favourite colour today. In fact, there is a French historian specialised in Middle Ages history, Michel Pastoureau, who wrote the history of the blue colour from the antiquity to the present. He says that for 65% of the people, blue is the favourite colour. In fact, it's the result probably of a very long tradition. The blue colour became popular only at the end of the Middle Ages. It's weird because before there was no word to qualify the blue colour. It became very important only at the end of the Middle Ages and it became the colour of God, the colour in the lapidaries that are the ancient treatises dedicated to the properties of gemstones Authors wrote that sapphire is the colour of the sky, so the colour of God. It became also the colour of Virgin Mary in the Christian religion. Here we can see a painting by a German painter, Stephan Lochner. It's a representation of a virgin with a child and she wears a blue coat. At that time, the blue painting was made with lapis lazuli powder. It was the most expensive pigment. It was reserved to the most important parts of the paintings. If you look at the virgin, she wears a crown, an amazingly beautiful crown entirely set with pearls and gemstones. When we look at the top of the crown, there is a sapphire. This sapphire is interesting the position because you can see above her, we have God, God the Father himself that is represented with the dove of the Holy Spirit, the Holy Ghost. In transition between the earth register and the heaven's register, we have the sapphire in between. The sapphire is the articulation between the earth and the divine in fact. On the right, we have a crown that was made by a very talented goldsmith in the beginning of the 17th century for the coronation of the Emperor Rudolf II of Habsburg in Vienna. This crown is very interesting because it looks like the crown of the virgin. What do we have at the top? We have a sapphire. It's the relation of the earth, the king, and God in the heavens. The blue became a very important colour and sapphire during the Middle Ages became probably the king of gemstones. Very positive colour, very important colour in the West. If we go to the East, it's a little bit different story. Here we are in India and you can see on the screen a jewel called Navaratna. Navaratna in fact means nine gems in Sanskrit, that is the original language in India. Navaratna is related to the Navagraha. Navagraha are the nine planets in the Hinduist cosmogony. We have a relation between the planets, the gods, and the gemstones. In Hinduism, the most important stone that is called currently Ratna Raj, that means the king of gems, is the ruby, the red gemstone. The ruby is in the middle of the Navaratna and it's related to the sun and to the god Surya. It's the most important gemstone for Hindus. We have also sapphire, a blue gemstone in the Navaratna. It's related to the god Shani and the planet Saturn. In Hinduism, Saturn is an ambiguous planet. It can bring bad things and also good things, but it's ambivalent. Only some people with a special astral chart are able to wear a sapphire without any danger. It's risky to wear a sapphire and most of the people prefer to avoid it. Blue colour and sapphire are not popular in fact in India. We have very few examples of pieces of jewels set with sapphire in the Indian world. Here we have two examples that are very rare. You can notice a pendant set with a sapphire as a main stone on the right. On the left, we have a portrait of Shah Jahan. He's wearing some jewellery set mostly with pearls, emerald and red gemstones that are probably spinels. But we can notice also sapphires and this is really exceptional. But we have to highlight that here we are in the Mughal context. The Mughals are a dynasty of emperors that settled down in India in the 16th century. They originated from Central Asia and they had many in common with the Persians. They shared the same language and they were Muslims like the Persians. So we are in a Muslim context so it's a little bit different than Hinduism. We talk about colour in a symbolic point of view but Laurent, what is colour physically speaking? Actually Marie-Laure, you need to have three parameters in order to precisely describe a colour. Hue, tone and saturation. Let's see them in detail right now. The first one is hue. Hue describes the colour as we speak. Blue, green, red, yellow. This is the primary hue but you might also have a secondary hue, an undertone. For example, here on the wheel, the hue wheel, you see you might have the blue and on the right you have violet-ish blue. So it means the blue has a small amount of violet inside until you reach pure violet on one side or pure green on the other side. So this is the first parameter. The second parameter is the tone. What is the tone? Tone is actually the amount of grey within the colour, within the hue. It describes the lightness or the darkness of the colour. We say it's a light colour or it's an intense, deep or dark colour. You see on this picture the tone scale with a different amount of greys from light to deep. Light, medium-light, medium, a 50-50 amount, medium-deep and deep. And of course below you have the sapphires. You notice that the one on the far left is light in colour and the one on the far right is deep, intense in colour. The third parameter, one of the most favourite when it comes to gems, is actually what we call saturation. Saturation is the depth of the colour, the intensity, the strength of the colour. On this picture you have four different sapphires with different tones but different saturation too. The one, the second on the left and the last one, they actually have the same saturation but different tone. Hence the fact that one is lighter in colour than the other one. So again, the saturation is the same but the tone is different. Then one is lighter than the other one. On the diagram where you have the ink, you see that you go from a weak to an intense colour describing its intensity. When it's very intense in colour, in gems we say it's vivid colour. And it's the most sought after. Yes. The most sought after for sapphire is pure blue and the higher saturation possible and it's very rare to find. So this is the vocabulary that we use when we talk about colour in a scientific way. Based on science, yes. But on the trade... In the trade actually, we have also trade names or commercial names that describe very subtle amounts and combinations of tone and saturation for the blue. For example, pastel, light tone as you see on the picture, cornflower, peacock, velvet, royal, going towards a higher saturation and a higher tone until you reach twilight, which is the darker tone on the picture. And in fact, this is the vocabulary used by one lab, the Lotus Gemology Lab in Bangkok. But in fact, sometimes some labs write also the name of the colour on the report. And here we have... It's written here. Yes. Let's take a moment to look at the report. On the gemological report, you will find many different parameters. The size, the colour, the measurements, the identification, of course, if it's a blue sapphire or another blue stone like, for example, acrymarine. The treatments, we will talk about treatments in a few minutes. Lab reports, the disclosed treatments. And sometimes, as you see within the red area on the picture, you have the trade names directly on the report that will describe the colour of the analysed sapphire. But in fact, what we have to highlight also is the fact that each lab has its own way to describe the colour in a commercial way. So it's important to know that a royal blue from the SSCF is not the same as a royal blue for the Lotus Laboratory. Yes, but they fall within the same range. So of course, you know, beauty is in the eyes of the... Yes, but sometimes it's... In fact, I think it's more important to see the stone and not to to trust what is written sometimes in a gem report regarding the colour. Yeah, basically, a gem report will... You have three pieces of information that are important. Identification, treatments. And also, we didn't talk about it, but you see here it's written origin, Kashmir. We are going to talk about geographical origin in a few minutes after treatments. Absolutely. Let's talk about treatments because this is really important. And I think it's the most important information in the gem report. Yeah, when it comes to sapphires and rubies, treatments are important. Actually, treatments have been done on rubies and sapphires since ancient times. So very, very long time ago. Antiquity. Exactly. So we will differentiate the modern treatments from the ancient treatments, the traditional treatments. Let's start with the traditional treatments, as you might see on this picture here, where the burner, we call the people who hit the sapphires, who hit the gems burners. You see here he's holding a blowpipe in his hand. The stone is actually located within the crucible and you see the fire on the coal, on the coke that is hitting the gem. He's going to bring oxygen in the area in order for the fire to be hotter. This is a traditional way of hitting gems. And heat is around 700 degrees centigrade. 700, 200, yes, with this technique. It's magical. It's technical. If you look at the sapphire before and after heating, it's just incredible. Yes. Actually, if you look at the Geuda sapphires from Sri Lanka, the before and after. So the before is the milky piece and then after heat treatment, it turns blue. In the case, in the very specific case of Geuda sapphires, you improve the color, but at the same time, you also improve the clarity. Absolutely. To me, I'm not a scientist, so it seems to be magical. Another traditional practice when it comes to heat treatment is the treatment done in drummers, as you might see on the pictures on the left and the picture on the right. You have the heat treatment done in a Thai furnace. You most of the time find those furnaces, those ovens in Thailand and Cambodia. You see the incandescent coal within the oven on the picture on the left. And on the right, you see the tower of bricks keeping the heat within the area. And of course, inside, there are the sapphires. And it's much more hot. Yes, hotter than the previous one. Here, like 1,000, 2,000, 300 degrees Celsius degrees, not Fahrenheit, of course. The picture in the middle is very interesting. Why? Because we are going to talk now about inclusions and as you might know, inclusions. So everything that are included within the gems, within the sapphires in our case, will give us a lot of information about the sapphire itself. Sometimes its geographic origin and of course, treatments. If the stone has been heated, for example, and in some cases, we will even know if it's this or that treatment. We will talk about that in a few seconds. So what do we see here? Actually, the sapphire subjected to heat, they will change. We saw color and sometimes clarity. But everything that is included inside, most of the time, it's so-called inclusions. Those inclusions, they also will be transformed. So this former crystalline inclusion that you see in the middle, just right here, has been heated. So it melted. And when it cooled down, it became a kind of bowl, a white bowl that we call, yes, Marie-Laure, we call it snowball or cotton ball. Hence, the fact that it's white. And there is a discoid fracture around due to the tension. In fact, because this mineral can't withstand the same heat as sapphire. Yes. But you're also right. Some inclusions, they will not fuse, they will not melt, depending on the temperatures of the oven. So when you look at inclusions, try always to at least see one or two. And if you can get the big picture, if you can analyze all the inclusions within the landscape, the gemscape, as I call them, if you can see inside the stone, try to see all the inclusions and see if some has changed due to the heat. Fascinating. Other treatments, more recent. Modern treatments. Now we are going to see three treatments, from the easiest one to the more complicated one to identify, because at the end of the day, what we want to do is to identify those treatments. Once we know the gem is a sapphire, then we want to know if this gemstone has been subjected to heat or not, or other treatments. In the case of sapphires, here we have lead glass with cobalt rich in the fissures and cavities. So the sapphires, they have been heated in an oven with a lead glass, and the lead glass that has cobalt inside, that will give the color blue to the glass, will infuse, will go inside the fissures and the cavities. You see very well on your picture. You see very well on the picture here, exactly. On that one, you also see the inclusion, typical inclusions that you might find in lead glass treated sapphires with cobalt. There are three types of inclusions you might find. You might find very round bubbles that are trapped within the glass, the glass being itself trapped within the sapphire. So you see some bubbles here, some very round, some a little bit more elongated. You also might find trapped bubbles, but flat bubbles. If the glass went through the fissures and the very small cavities, the bubbles, they will not be round because they don't have the space to be round. So they will be flat. So this is an indication of such treatment. And of course, you will have color concentration, meaning that the cavities, most of the time the big cavities, they will hold the glass and the glass is blue. So you will have patches of blue like that within the stone. The good news is this treatment is quite easy to identify with just a look and a good training. But sometimes, in fact, it's a composite stone. Sometimes there is more glass than sapphire. Yes. This is the very fine line between a single stone, which is a treatment, and more than two stones, which is a composite. You are right. The second treatment is diffusion. And here we will diffuse within the sapphire. We will diffuse the elements that are responsible for the color. We have seen before that blue sapphires, they are blue because of iron and titanium. So we diffuse iron oxide and titanium oxide within the stone. This diffusion process will give the sapphire a blue color, but the color is only very, very, very shallow. It's just on the surface and subsurface. In other words, the core, the inside, the very inside of the sapphire is not blue. It's still colorless, as you might see on the picture with the stone before and after treatment. Absolutely. So it's made on polished, already polished sapphires. Yes. So if you see such a stone and you have to repolish, just be careful, don't go too deep, otherwise you will lose the color. Again, it's the inclusions that will help us, help the gemologists to identify the treatments. As we see here, we see a kind of similar inclusion that we have seen before, but here there is no glass. So we see a color concentration around those surface-reaching fissures and cavities. So they have been cut during the polishing process and you see that actually patches of blues again within the stone. The stone is unevenly blue, but if you look with a loop or microscope, better even have a look in immersion. So you immerse the stone in a liquid, you will see those kinds of inclusions. If you see this, it might have been subjected to a heat treatment with diffusion. So it's quite easy to see. But there are other treatments, especially one that is very difficult to disclose for practical gemology. We really need to go to a gemological laboratory. Yeah, exactly. The third one, the most complicated to identify with just a loop. And even if you have a good training, because in that case you need advanced instrument, is the treatment done by diffusion of light elements. For example, beryllium. Beryllium is a very, very small atom compared to titanium, iron, aluminium and oxygen. So beryllium will dive into the sapphires and will go to the core of the sapphire. So it's not just on the surface, it's also within the sapphires. It's called diffusion. Exactly. We call it lattice diffusion. So here you see the sapphires before and after treatments. The colours are actually before treatment quite nice, but look at the candy colours on the after treatment. Probably more appealing for the market. Yes, exactly. More nicer colours, more intense and more vivid. You see the oranges here, they are quite vivid, so very high saturation. One important thing, two important things to say. The first one is you need very high temperatures. You see the furnace. This is a picture I took in the Gemological Institute of Thailand when I was in Bangkok. And look at, read the temperatures that you need, 1,150 degrees. So this treatment requires a very high temperature first. Second, as you said, you cannot really identify this treatment with just a loop and some knowledge. You need to have access to advanced instruments and where are they? Most of the time in labs. So in fact today on the market, 95% of the sapphires are treated with one treatment or another. Of course, the most beautiful sapphires, the most sought-after sapphires are untreated and they are very rare. It's very difficult to find a very beautiful colour without any treatment. And here we have the world auction records for sapphires. We have different kinds of sapphires, all very beautiful and even in colour. Very large stones and from different localities, as you can see. And we will talk with Laurent after of different deposits for sapphires. And you can see the world, the auction records. So we give them always in total price and also in price per carat. Do you want to say something about that? Yeah, just one thing. Please look at two things, the size of the sapphires and the price per carat. Very interesting to see that the Kashmir one, we'll talk about Kashmir in a few seconds, is a bit less than 30 carats for 243,000 US per carat. Look at the two other stones, they are way bigger. And look at the price per carat, five times less than the Kashmir one. And there are many reasons for that, but one specific reason we will talk about in a few seconds. It's related to Skesh City, maybe? Yes. So it's important to be aware that in high jewellery we don't use treated sapphires, only completely natural sapphires. No treatments. No treatments. So let's start our journey around the world to discover the different sapphire deposits. So here we have a map of the deposits today. So historically speaking, the first sapphires, the first deposits that are of importance are Sri Lanka. And in fact, in Asia, Southeast Asia is very important for sapphire deposits. We found historically also sapphires in Myanmar, in Thailand. And of course, in the north of India, we have also deposits in Vietnam and in Cambodia. So very important, in fact. Some deposits are almost empty today, but some still producing, like Sri Lanka. Sapphire deposits in Australia, they were of importance at the end of the 20th century before the discovery of Malagasy sapphires. Australia was the first world producer in quantity. In the US, sapphires were discovered in the 19th century and they are still in exploitation in the Montana state. But we don't see them worldwide. They are sold only on the American market. The last area where we discovered sapphire is Ethiopia. And in fact, East Africa is today probably the most important place for sapphires with Tanzania and especially Madagascar, that is the first world producer today. Let's start the journey around the world and in time also, so Sri Lanka. Sri Lanka is the place where sapphire has been produced since antiquity. So the most productive place for sapphires. And you can see on the left, it's a ring set with a Sri Lankan sapphire that was discovered in a city, the city of Iqanum in Afghanistan, a city founded by Alexander the Great in the fourth century before common era. Alexander the Great played a very important part in the international gemstone trades because he opened the commercial routes between the West and the East, what we call the Silk Road. And we know that it was the start of the international luxury trade. During the Roman times, sapphires became more and more available in Europe, thanks to the Silk Road. And we have an example of a Roman cameo in sapphire on the right. So it dates back from the first century. And in fact, we know that at that time, there were Roman counters, commercial counters in India and also in Sri Lanka. So it was really important. The ancient word for Sri Lanka in the Western world was Trapoban. So you can see the map here. It's the cosmography of Ptolemy. And so it was the name given to the island in the West. And the Arabs and the Persians called this island Serendib or Serendib. And it gave the word Serendipity, that means happy encounter by chance. And it gave the word to the rare stone Serendibit. Yes, I didn't know it. I learned many things with you. So this place was described as the paradise of gemstones. For example, in the tale of Sinbad the Sailor, that is an Arab tale from the 8th and 9th century. And also Marco Polo in the Book of Wonders talk about the island, but he called it Silam, but we'll give the word Silam later. Sri Lanka gave also the largest known sapphire and so Laurent told us about the fabulous star sapphire of 563 carats, the star of India that is preserved in New York at the Natural History Museum. And I discovered during the preparation of this talk that a very large sapphire is preserved also in Dresden in the Green Vault. It's a more than 500 carat sapphire called the Nose of Peter the Great. And regarding the faceted transparent sapphire, in fact this one, this 468 carat Sri Lankan sapphire is probably the largest one. It was purchased by Cartier in 1913 and Cartier sold it to the Queen Mary of Romania in 1919 and she wore it as a pendant as you can see on her portrait on the left. It was sold by Christers in 2003 for $1.5 million, so it's not a very expensive price regarding the prices that we can see today on the market, even at auctions. An amazing stone. There are other localities that are very important historically for sapphires and the magic word is? Kashmir. Of course. The name on itself, it's a poem. Yes, Kashmir sapphires. Kashmir sapphires, they are intense, super nice blue, very vivid, very rich in colour, but they have a specificity, those sapphires, they have a velvety appearance that you call? A sleepy blue. A sleepy blue and this sleepy blue which is quite specific of this locality that gives this amazing look of the sapphire is actually due to some inclusions. Here again we talk about inclusions, everything trapped within gems, and you have here on the picture the origin of this sleepiness, the origin of this velvety look of the sapphires, those whitish clouds that are within the sapphires. Another important locality when it comes to gems is of course Burma, Myanmar, that gives a lot of sapphires for many, many, many centuries, sometimes big sapphires as you see here with the Rockefeller sapphire which is 62.22 carats, quite a big sapphire, unheated. Absolutely. Yes, and recently 2010 and plus a mine in Burma that I had the chance to visit in 2020, Boma, which is the north of Chapin, Chapin being the west of Mogok, the Ruby Valley. Here there is a picture of the north Boma because Boma is a so big mine that you have the north and the south. This is a picture of the north, and the sapphires that came here were really nice, really, really nice, and we saw them arriving first in Bangkok market. And why do you have green and blue color on the picture? Yeah, actually just below those tents they are mining, so they are digging holes because this is a primary and secondary mining mine. So you told me that, I don't remember if the green is empty and the blue is currently in production? Yes, the green, the main one, this one, is the one where we went below and is actually was running when we when we went there to visit the miners and get some samples for collections and teachings. Really interesting. The last locality is of course Madagascar, the red island, beautiful, very famous for the landscapes and the variety of gems, one of the most blessed country when it comes to gemstone. We really like this country. And they also, Madagascar provides very nice intense color blue sapphires, as you might see on those two 15 carats plus, coming from the north of the capital, Antananarivo. Exactly. Here you see the map of Madagascar and you see that the capital is just below the the name Madagascar and above you have a very wide area that is producing gems with some very famous localities like Did, Bementi, and of course Andilamen when it comes to rubies. And in the south we have also very important deposits like Ilacac, that is probably the most famous place in Madagascar for sapphires. Yes, worldwide known for the area because you have also blue sapphires but you also do have other colors like the yellows and the greens and the pinks, a lot of pink, very nice pink sapphires coming from this area. Yes. So to end this conversation with Laurent, it's a present for you, the most beautiful creations, among the most beautiful creations with sapphire, contemporary creations. So this necklace by Van Cleef & Arpels, it was the high jewelry collection last year called Sous les Etoiles, Under the Stars, and this necklace, Trésor Astral, is set with two amazing sapphires, perfect in color, perfectly matching. One is from Burma, the other one from Sri Lanka, but we have the same color, same quality, amazing size too. And what I like too is, it's the beautiful bridge by Cindy Chao, we are really fond of star sapphires. We do. In addition to color and clarity, we talked about those two parameters before, when it comes to star sapphires, you also have the quality of the star, the quality of the legs, the intensity of the star, and of course directly linked to the inclusions, so the clarity of the matrix, the clarity of the sapphire itself. So it's really an exceptional stone too. Yes. So we will in a moment receive your questions, thanks to Gislain, but I would like to talk to you about a forthcoming conversation next month. It will be a conversation between Carol Fareso, she's an archaeometallurgist, specialist of the Peru civilizations, and she was the curator of a very beautiful exhibition in Paris about Machu Picchu, and with our dear colleague Paul Paradis, who is an art historian and professor at the School of Jewish Arts. So it will be about jewelry in ancient Peru. So now we are ready to answer your questions, so with Laurent we will have a look on the questions given by Gislain. Thank you for your attention, we are going to talk about, take your questions, so we have a lot of questions right now, some linked to history, that Marie-Laure will take care of, and some linked to more about the science behind heat treatment, for example, that I will take care of. You want to open the question session? So the question is, why are sapphires so associated with royalty? In fact, blue, and the blue color became the color of the King of France during the 12th century, if I remember well. So the emblematic colors of the King of France are blue and gold, so we have a gold fleur-de-lis and a blue color. So I think it's related to the development of religion, and the idea of blue as the color of sky and god. Let's talk about clarity, we have two questions actually, it seems that we have a lot of questions about how the heat treatment will improve clarity of sapphires, so let's go back to geuda sapphires. What are geuda sapphires? They are actually translucent white sapphires, so after the heating process, the sapphires will change the color and the clarity. The color will turn from whitish to blue, this is okay. How does it improve the clarity? Actually, this whitish, the color of the geuda sapphires, the fact that they are whitish, this is due to very, very thin, long needles within the sapphires. When you heat, this is rutile, exactly the same origin. Titanium oxide. Titanium oxide, exactly, so the same origin that gives birth to the star on the sapphire. So when you have a whitish sapphire with a lot of those thin needles, you cannot see through, because you have a lot of needles. Once you have heated the stone, the needles will dissolve within the sapphires, improving the color and the clarity. And if we want to go further, actually, you obtain, achieve to get the blue, because of the dissolution of the rutile, because as you said, it's titanium oxide. So you have already iron within the sapphires, but it's not blue, so you titanium in order to have this blue color, we talked about it. So when you will dissolve due to heat treatments, the titanium oxide, the titanium will go within the structure, and then you have titanium and iron with the intervalence charge transfer that gives the blue color. So in that case, you have improved both color and clarity. There is a question related to the question you just answered. Can we say darker blue sapphires contain higher numbers of iron and titanium atoms? Sorry, I was reading another question. Oh, sorry. The dark, the dark, dark hues are related to iron. Yeah, the more iron you have, the darker it is. Let's put it that way. Yeah, the more titanium you have, the most vivid the color is. No, there is no direct relationship between titanium and color, more about iron. And in the case of sapphires, iron and titanium together. There is a question from Japan, what kind of material creates a star effect? So as we have seen, talking about rutile just now, actually those very fine needles within the sapphires, they will be within the structure. And when you have enough of those needles, and if you cut, properly cut the sapphire, not as a faceted gem, but as a cabochon, then you will have this effect appearing. What is the identity of the inclusion substance? This is titanium oxide called rutile, R-U-T-I-L-E. Another question for you, regarding the temperature used in treatment process, is it 900 to 1800 degrees? And is it the same for ruby? So yeah, corundum actually melts at 2050 degrees. So it obviously has to be below. But you have low temperature treatment, medium temperatures, and high temperatures. Some treatments, you cannot achieve them if you don't have high temperatures, like beryllium treatment, for example. For the treatments in the batacubala, the blowpipe in the coal, the temperatures are way lower. So it depends on the material, its origin, and of course its chemical composition. This is a very complex science, shall I say. Heating gems is complicated. And every time there is a new deposit, then you have to adapt your heating technique to see if it works or not. And also on the market today, we hear a lot about the low temperature treatment, but it's very difficult to disclose. What is the temperature for low temperature? It's not an exact, we don't know precisely, but we say usually below 1,800 to 1,000 degrees. It's considered a low temperature treatment. Very difficult to see with just a look. And in some cases, most of the cases, you actually do need advanced instruments. In Mozambique, for rubies, they practice heat treatment at 500 degrees. Depends what they want to achieve, yes. Another question from Japan. Why does color and transparency change when heated? The answer is the certificate does not state whether the stone is heated or not. Can you tell if the stone is heated just by looking at it? There are two questions within one. The first question is about the certificate. Yeah, the main purpose of having a report from a lab is to identify the stone, if it's a sapphire, a aquamarine, or a blue other gem, like a topaz, for example. First. Second is about treatments. All the reports, they have to disclose if a stone has been subjected to any treatment, and if yes, which treatment, and sometimes to which extent. The second question within is this question is, can you tell if the stone is heated just by looking at it? Most of the time, I would say yes, with training and the loop. This is actually what gemologists do. But in some cases, you do have to have access to advanced instruments, like Raman and other advanced instruments. And those instruments, they are available in the labs. Infrared, FTIR, and UV visible spectroscopy, and so on. Are blue sapphires more valuable than other color sapphires or not? Same size and treatment or not? Okay. In fact, the most valuable corundum is ruby, far above, in terms of price. Parameters being equal. Yes, of course. You're right. It's important to precise it. Ruby is the most expensive corundum. It's the rarest color after blue, in terms of price. We have paparazzo too, but it's very sought after and very expensive and very rare. Paparazzo means lotus flower in Sinhalese. That is the most common language in Sri Lanka, but it comes also from Sanskrit. And it's a mix of pink and orange, but it's a trade name. So, depending on the labs, some sapphires will be described as paparazzo by one lab and not by another lab. So, it's always complicated, like all the trade names to me. So, one last question. Are pink sapphires the rarest? They're actually quite rare. Very, very nice pink sapphires coming from Madagascar or coming from Sri Lanka or coming from Burma. When the color is very saturated, when the color is very vivid, very profound, very deep, they are actually extremely rare and very beautiful. Yes. I think for blue sapphires, probably these blue sapphires are really more sought after in the West. Yes. And paparazzo in India, Sri Lanka, also in Japan, it's more popular in Asia. We do like all the colors, as you understood, when it comes to sapphires. It's a question for you. What level of magnification are your pictures of the inclusions? Thank you for asking. So, I do photomicrography. So, I take pictures of inclusions within gems as an educational tool, but also as an art. Most of the time, I am within 50x, so a magnification of 50 times, up to 150, depending on the microscope. Very important to answer. Is a heat-treated sapphire less valuable than an untreated sapphire? Would you like to answer? I think, in fact, usually, treatment gives more value to the stones. And some of them, especially with the kind of treatments, as Laurent explained, the lead, glass, cobalt filling, for example. Usually, this treatment is applied on sapphires that are completely impossible to sell on the jewelry market if we don't make this kind of treatment. So, usually, the treatment, it's an enhancement. Also, it gives value to a stone. But, of course, for an equal color of heat-treated sapphire and untreated sapphire, the price of the untreated stone is much higher. But depending on the treatments, the price will be different. Yes, among treatments. The main goal of a treatment, of enhancing gems, is to increase their price by increasing their beauty. So, we have still one minute just to tell you that the conference will be available on YouTube as a replay. And I would like to thank the team. I would like to thank you for this presentation. And, of course, the public, thank you for being here on your time. And it has been a very great pleasure sharing knowledge, learning a lot of things from you, Marie-Laure. And thank you very much. And see you online very soon. Thank you so much. Thank you. Thanks to all. Bye.