NEWSLETTER No. 9, March 2010

Transcription

1 NEWSLETTER No. 9, March 2010 Dear SSEF Alumni members and friends, I am happy to see that the economy has been picking up gradually and that many jewellery shops have reported a positive trend in sales even in the first couple of months of the year. I trust that this tendency will continue throughout the year. We from the SSEF Alumni team have some interesting events coming up in the not-so-distant-future and of course are looking forward to seeing you all at these presentations. As always, we are more than happy for any feedback that you might like to share with us so please don t hesitate to write or call. Wishing you all good health and happiness, best regards, Leon Ascot Contents: Gemmological Articles and Notes: 2 Abalone, Conch and Melo: exceptional pearls from marine snails Michael Krzemnicki 8 Expedition to the mines of Luc Yên, Vietnam Flavie Isatelle About SSEF Alumni: 16 Membership and contact details SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 1

2 Gemmological Articles and Notes: Abalone, Conch, and Melo: exceptional pearls from marine snails Dr. Michael S. Krzemnicki In this third and last part of this small series of articles on natural pearls (see also issue No. 2008/10 and 2009/01), I would finally like to present the exceptional pearls of marine snails (gastropods). There are species that produce nacreous pearls (e.g. Abalone), but also snails, which produce non-nacreous porcellaneous pearls (e.g. Conch and Melo). Pearls from marine gastropods are rare and thus often quite expensive. They are often distinct in their shape and colour, which makes the designing of jewellery using such pearls quite a challenge. But it is their uniqueness that makes these pearls very attractive for pearl lovers. Fig 1: Necklace with Conch pearls, alternating with small diamond briolettes. Abalone (Haliotis): The marine gastropods of the Haliotidae-family are found worldwide in coastal waters, with the exception of the western part of the Atlantic Ocean. Most abalone snails are found in rather cool climates in New Zealand ( Paua shell ), Australia, South-Africa, Japan and the northern part of the American West Coast. Fig. 2: Partly polished shell of an abalone, showing intense interference colours. The holes in the shell are very characteristic for abalones. KWO Grimselstrom SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 2

3 The shape of the abalone shell resembles a human ear (thus the synonym sea-ear or Venus -ear ). It shows a series of small holes, through which seawater circulates. The shell attaches itself on intertidal rocks near the shore using its strong adductor muscle (foot) and it feeds itself mainly from algae. The meat of the abalone is highly sought after, especially in Asia. The prevalence of snail hunters is the reason why in certain regions the population of abalone snails has dramatically. Nowadays, the large majority of abalone snails destined for cooking are cultivated in abalone farms. The shell of the abalone shows very intense blue green to pink interference colours. These colours are a consequence of the structure of the shell, which consists of very fine aragonite platelets (calcium carbonate). Spectral colours are partially extinguished or strengthened due to multiple reflections of white light on these fine aragonite layers. The result of this is marvellous iridescence. Natural pearls (or natural blister pearls) are only rarely found in wild abalone snails. The cultivation of pearls in abalone shells is very difficult, compared to the pearl farming with oysters or freshwater mussels. However, it is rather simple to slide a small half-bead along the inner shell surface inside the abalone- this can consequently produce so-called Mabé cultured pearls. The natural abalone pearls are usually irregular in shape (baroque); they are often found having a distinct horn-shape. Queen Conch (Strombus gigas): Most of the ca. 50 conch species of the Strombidae-family live in the southern Indian and Pacific region. Fig 3: Natural abalone pearls and blisters However, the species best known in the pearl trade is the queen conch (Strombus gigas), which is found in the Caribbean Sea. This large marine snail may be more than 20 cm long and weigh 2.5 kg. The animal protects itself with its massive shell. Fig 4: Queen Conch shells with some small conch pearls and a cut piece from the shell. SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 3

4 The Conch feeds itself mainly from algae, which the animal grazes from seagrass and the sandy soil. Conch snails are hunted in large numbers as comestibles. This is why the snail is nowadays partially protected. Conch pearls that are found by local fishermen rarely represent much more than a small additional source of income. Up to now, there is no cultured pearl known to have originated from conch shells. The colour of the queen conch (strombus gigas) varies from white (external rim) to intense pink (inside of the shell). This also becomes obvious when a piece of the shell is cut off (fig. 4). Therefore, it is not astonishing that conch pearls may also show this variation from pink to orange and light brown to white. Fig 5: Conch pearls showing partial colour graduation and a distinct flame structure (pearls on the right). The characteristic feature of the conch shell and the conch pearls is not only its attractive pink colour, but also a distinct surface texture, which is called flame-structure. This is a result of densely interwoven bundles of fine aragonite fibres (fig. 6). This structure causes a fine and silky sheen when light is reflected on these fibres and also makes conch shells extremely resistant to fracturing. Fig. 6: Flame-structure of a conch pearl (magnification 30x) and a high resolution picture taken with a scanning electron microscope, showing the densely interwoven aragonite fibres on a conch shell (fractured surface). SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 4

5 Melo Melo (Volutidae family): The Melo gastropods mainly live in tropical waters along the coast of South China, Vietnam and up to the Andaman Sea in Thailand and Myanmar. The shell can grow up to 20 cm, but is much thinner than that of the conch shell (fig. 7). Both the Melo shell and the Melo pearl show a similar structure of densely interwoven aragonite fibres (similar to the conch) and the shell itself is also quite resistant to fracturing. Fig 7: Shell of a Melo Melo snail. The Melo pearls are usually orange to light brown in colour, with a fine to spotted flame-structure. Apart from smaller baroque-shaped pearls, this species is especially renowned for its very large and perfectly round Melo pearls (up to the size of a golf ball). Fig 8: Collection of large Melo pearls. The largest is 30 mm in diameter and weighs 190 cts. SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 5

6 For most customers, Melo pearls are typically far out of reach as they are much too expensive, taking into account not only their rarity, but also their size (and weight). There is, however, a small clientele of pearl collectors and lovers, who pay whatever is asked to buy such rare pearls. So far, no cultured Melo pearl is known. But seeing as both Melo and Conch pearls fetch such high prices, it is not astonishing that (so far unsuccessful) attempts have been made, hoping to produce cultured pearls in these marine snails. Fig. 9: Flame-structure of a Melo pearl. Pearls from marine snails, exclusive and exceptional: Apart from some delicious cooking experiences, people usually do not like slimy snails. But most astonishingly, a great number of marine gastropods are able to produce exceptionally beautiful pearls. The species abalone, conch, and melo, which have been presented here, are among the most appreciated pearl producing animals. Natural pearls can, however, also be found in many other marine gastropods. The rarity of these pearls and their specific appearance (e.g. porcellaneous ) are certainly different from what people normally conceive a pearl to be. It is exactly this diversity and individuality, which increasingly fascinates and motivates jewellery designers into creating unique jewellery items using natural pearls....and finally: With this third and last part about pearls from marine snails, this small series of articles on natural pearls finds an end. For many years, we have been analysing all kinds of pearls at the SSEF Swiss Gemmological Institute on a daily basis. For our clients, the main focus is the question of whether the pearl is natural or cultured. It is only in a subsequent step that the question may arise from which species a certain pearl originates. Unfortunately, a definite identification of the species is not trivial, sometimes not possible at all. But if we take into account the great diversity of all existing freshwater and saltwater shells, this may not be too astonishing. It is only by continuous research that we can gather new information and expertise. If these articles have aroused your interest in pearls, we would like to invite you to participate in a pearl course at the SSEF Swiss Gemmological Institute. Apart from a very detailed introduction into pearl formation and farming, you will have the worldwide unique possibility to analyse pearls yourself with advanced pearl testing methods such as radiography, X-ray luminescence, Raman, to name but a few (course programme see Apart from the pearl course, we also offer a very informative educational CD-Rom about pearls (tel or gemlab@ssef.ch). SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 6

7 Finally, I would like to thank again Thomas Hochstrasser ( for providing many natural pearls to the Swiss Gemmological Institute SSEF. Furthermore, I would like to thank Laurent Cartier and Pierre Lefèvre for translating these articles into English and French. Figure references Photos: H.A. Hänni / M.S. Krzemnicki, Swiss Gemmological Institute SSEF and M. Düggelin, Institute for Microscopy, University Basel, Switzerland. SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 7

8 Overview Expedition to Luc Yên, Vietnam January 2010 Where the toughness of miners lives meets the beauty of stones Flavie Isatelle Those who come walking into the deep mountains of northern Vietnam will understand why the French were defeated during the Vietnam War. I had never encountered such tough conditions in an expedition to the mines! Rough muddy roads accessible only by motorbike, stiff sharp paths into the mountains; and at the same time such a stunning insubstantial landscape! It looks like the pastel colors of the lands influenced the colors of gemstones: from blue valleys and trees to a pink sunset sky due to the constant cloudy weather and weak incoming light. Blue spinels and pink to red rubies are also found, matching their entourage as if they were meant to be formed there. And local people, especially miners are alike: tough in their mind and warm in their heart. This expedition was certainly the most moving experience I have had, as much by the beauty of stones and scenery as the tough living conditions of miners over there. It was also the first time I shared lunch with miners, a simple nice lunch with only Vietnamese-speaking people! I learnt how to drink shots of rượu rắn (rice wine), how to appreciate the bitter tea at the end of the meal and how to politely refuse to eat BBQ rat! Fig. 1: Location of Luc Yên mining area (around Yên Bái). Google Earth Introduction of the Mining area of Luc Yên: Luc Yên mining area is located around the village of Yên Thế, which is in the district of Yên Bái Province, in the Northeast of Vietnam. Yên Bái is located around 180 kms to the northwest of Hanoi. Actually, local people say Luc Yên instead of Yên Thế, which can create some confusion about the geography. The mining area of Luc Yên is part of the Himalaya Belt, which was formed during the collision between Eurasian and Indian plates over -45Ma. So the terranes found in this region are metamorphic, mainly marble, schists and gneiss. Fig. 2: On the road to Luc Yên, blocked by a truck stuck on the road SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 8

9 I happened to study marble-hosted rubies from Southeast Asia during my final year at the National School of Geology in Nancy, France. I actually studied the synthesis of corundums in melted salts, by recreating the conditions of pressure and temperature and mixing components that play a role in the formation of marble-hosted rubies. That was one of the main reasons I wanted to go there and visit the mining areas around Luc Yên. Let s get started: I left Hanoi early in the morning on the 23rd of January to catch a bus from Mỹ Đình Bus Station which took us to Luc Yên. Nine hours later and one hour stuck behind a truck stuck in the mud because of the bad state of the road and the heavy rains which had been continuous for the past week. I finally arrived in the small village of Yên Thế that evening. There I met Philippe Ressigeac (a young passionate French gemologist from GIA) and Lou-Pierre Bryl (a young passionate French Canadian gemologist, FGA) who were there for two days, trying to see and buy some stones. P. Ressigeac introduced me to his local guide and motorbike driver, Mr. Chuẩn, and we hiked together through the stunning mountains of Luc Yên, despite the bad weather, rain and cold we endured on a daily basis. Fig. 3: Mine Thiến valley Miner holding the water pipe used for washing. Fig. 4: Parcel of spinels and rubies from Cống Trỏy I SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 9

10 Mining areas visited: In three days spent in this region, we managed to visit eight mining areas, namely Cống Trỏy I and II, Mine Thiến, Con Gan, Bậi Thai, Bậi Chuới, Bậi Sợn and Bậi Cat. Mine Thiến: We left around 10:30am with Philippe Ressigeac, and our two motorbike drivers including Mr. Chuẩn, our local guide. We went through the mountains surrounding Luc Yên and arrived at Mine Thiến where some people were mining rubies (zoubi in Vietnamese), sapphires, green and pink tourmalines, spinels (sitinel or sitilen in Vietnamese), all of small size but quite good quality. Two groups of two to three people were working, digging and washing the muddy gravel amidst the rice paddies. Fig. 5: Parcels of rubies found in Cống Trỏy II, used mainly for paintings. Cống Trỏy I: Then we climbed up to Cống Trỏy I, where there is a primary deposit for spinels and rubies in marble. We could not see the big marble slope where they are blasting the big blocks because the weather was too cloudy and misty. About five miners live permanently there with a woman in charge of sales (not cooking!). Violet to pink spinels are found there in marble and in association with pargasite and humite. This is the same type of paragenesis than is found in Mahenge in Tanzania. Fig. 6: Mineralogy of spinels found in Cống Trỏy I, in marble matrix SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 10

11 We shared lunch (ặn cợm which literally means eat rice ) with miners, and of course drank some rượu rắn and the bitter and strong Vietnamese tea at the end of the meal. Cống Trỏy II Cống Trỏy II is a secondary deposit contrary to Cống Trỏy I, so gravel from the river stream is washed, and rubies and spinels are sorted out. There were only a few people mining. Stones sorted out are used mainly for paintings, a very popular activity in Luc Yên, which consists of drawing a landscape or character by sticking small stones on a special type of paper, according to their color. Further down we saw a few other places that had been mined, and we could see the hump of gravel on the river side, but there was nobody working there. On our way down, we could admire the bottom of the marble slope of Cống Trỏy I, called Cống Trỏy (= sky gate ), whereas the top was hidden in the clouds. Co Ngan Late that afternoon we reached the stunning valley of Co Ngan, which, even with bad cloudy weather conditions, looks amazing. Two groups of three to four miners were working, washing gravel form the ground and sorting out spinels (pink and blue), rubies, sapphires and tourmalines. Fig. 7: Mining in the stunning valley of Co Ngan: miners digging into the mud before washing gravels and sorting out commercial stones. Bậi Thai Choan Thống The second day I was left alone with Mr. Chuẩn to explore the other side of the valley and we went to Bậi Thai (Choan Thống). It was the biggest mine I saw during this expedition. Eight miners were working there, seven days a week. This mine was mechanized with three pumps (one water pump, one mud-pump and another one that was out of service when we were there). They sort out rubies, later used mainly for paintings as they are very small in size. However, quality is already much better that in Cống Trỏy II. Mr. Nam, the boss, told me that if there were no tektites, there were no rubies, and vice versa. I could witness the presence of tektites in the bamboo basket used to sort out stones all together, with some rubies. However, I do not see why the presence of tektites would imply in any way a presence of rubies. They have two different ways of formation and two very different origins. So, either it is a coincidence that they happen to be found at the same place, or they are mixing up two different stones that had nothing to do with each other. Moreover, I have been told that they were mining only rubies (not sapphire), yet there was a sapphire-shape ruby in the bamboo basket too. I know from experience that ruby can take on the same crystal habit as sapphire. However, this is quite an interesting thing to come across as it is not common. SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 11

12 Essentially, they dug an open pit of 20x20m and 5m deep. The water-pump takes water from a swimming pool nearby and is then sent under pressure into two pipes used to dig. The mud pump takes mud and small gravel (big ones are taken out by both two miners and a sieve at the entrance of the pump) and sent to the washing plant where there is another sieve and a miner ensuring it functions correctly. Rubies are washed into the jig (fixed jig) and water is sent back to environment. The boss, Mr. Nam, stays at the mud pump because this last one needs to be stopped, cleaned and restarted every once in a while when it becomes blocked by gravel too large a size. Fig. 8: Mineralogy of spinels found in Cống Trỏy I, in marble matrix Fig. 9: Panorama of Bậi Thai mining area SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 12

13 We shared lunch with miners again, and it was a very simple but joyful lunch. It appears to me that there are two main problems in this mine or maybe two things that could be improved. The first one is the mudpump that blocks every 15 minutes, which is a waste of time and energy (stopping and restarting a pump consumes a lot of petrol). So maybe only one water pump would be enough to dig (as there is only one pipe to remove mud) and the second miner could work more efficiently by helping to extract the gravel. Also, if there is more water coming into the pit than going out, the mine will be flooded. There were actually about 50 cm of water down there, is this because of the rain or the water coming from water pipes? It would be interesting to go back during the dry season to check this out. The other point is that miners work every day, so with 8 miners they could all have a day off one after another so they would see their family and have a rest, and it would not affect the production of the mine; in my point of view. Fig. 10: Flow sheet of the mining organization/ exploitation of Bậi Thai Bậi Chuới In the afternoon, we went to Bậi Chuới to meet Lou-Pierre Bryl and Phillipe Ressigeac. However, nobody was working there so we came back to Luc Yên. Fig. 11: Mining camp of Bậi Sợn SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 13

14 Bậi Sợn The last day I left off alone again with Mr. Chuẩn to climb the steep mountain leading to Bậi Sợn. It was not only steep, but also slippery as it was so humid. Jumping from one sharp-edge block of marble to another, crossing deep holes of several meters in size on a very slippery wooden stick was kind of an adventure! I would like to thank Mr. Chuẩn very much as he helped me and waited for me the whole time. Besides, it was quite disappointing when some miners overtook us, wearing flip-flops and carrying heavy pieces of wood, I felt like they were flying past us! So we arrived at Bậi Sợn late in the morning to see the poorest mine I have seen. No machines, 4 miners hand digging between blocks of marbles looking for the very famous blue spinel. Production is very scarce but stones are certainly beautiful. Fig. 12: Light blue to violet spinel from Bậi Sợn : the Legend! Again we shared lunch with them, which was composed of BBQ rat, the usual rice and some cabbages. People there are working every day, eating, sleeping in a wooden hut, which hardly protects them from the rain, and they almost never come back home. Are the living conditions of these miners counted in the value of the stones? I am not sure about that. Bậi Cat After lunch we climbed down (way more difficult that climbing up!) and went to Bậi Cat, where I was told that the best rubies in the area can be found. It is true that the rubies look nice, and their size is a little bit bigger than what I saw before. Mr Cao, the boss, works here with 9 other miners. They dug an open pit of 10x10x4m. It is a secondary deposit but they have to take out the many big blocks of marbles buried in the ground using drills for that and then carry them on a stretcher. Fig. 13: Bậi Cat ruby mining area. At the back one could see miners drilling into big blocks of marble, at the front miners carrying some heavy pieces from the blocks. Fig. 14: Rubies and Sapphires sorted out at Bậi Cat SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 14

15 After a cup of tea we came back to Luc Yên and I said goodbye and thank you to Mr. Chuẩn, Philippe Ressigeac and Lou-Pierre Bryl as I was going back to Hanoi early the next morning. Conclusion: Going to Luc Yên was, as I said in the introduction, something I have wanted to do for a while and I was not disappointed, in fact I was happily surprised. What I pictured after Tanzania, Madagascar and Southeast Asia was far from the reality. The living conditions of miners there were worse than I expected. To say it simply, they have nothing. A lot of work has to be done over there. I also went there when there was almost nobody working; maybe when they have more miners and more production, things are different. As a beginner in this world, I could not see any of the nice stones they keep for buyers; however those I saw were quite nice. It would be interesting to know how many big valuable stones they sort out per month or per year, just to see if mining is at all viable. Exploring the mountains around Luc Yên was also a very moving experience; sharing simple lunch with miners, trying to talk to them in my very poor Vietnamese and seeing this big smile always on their faces, these eyes full of hope and pride that I will never forget. I thank all of them for being so patient and kind with me. About the author: Flavie Isatelle Geologist & Mining Engineer A. G. Many thanks go to Vincent Pardieu for his valuable help, advice and suggestion of contacts. ( Figure references: Flavie Isatelle, 2010, Fig.15 P.Ressigeac Fig. 15: Cảm ợn và tốt sư may mắn! (which means in vietnamese; good luck and thank you!!) SSEF Alumni Newsletter No. 9 info@ssef-alumni.org page 15

16 SSEF Alumni Membership: How to become a Member of SSEF Alumni? The SSEF Alumni Organisation is open for former participants of courses at SSEF Swiss Gemmological Institute, FGA students, and further interested persons in the gemmological community. The SSEF Alumni is intended as a platform for the exchange of information and for continuous gemmological formation. Membership fee is 50 Swiss Francs per year. Please see our website for more information ( or contact our President, Leon Ascot at info@ssefalumni.org, when you would like to participate at exclusive SSEF Alumni events and to receive the highly informative electronic newsletter several times a year. Editors: Laurent E. Cartier Department of Environmental Sciences, University Basel Bernoullistrasse 30, 4056 Basel, Switzerland laurent.cartier@unibas.ch Dr. Michael S. Krzemnicki SSEF Swiss Gemmological Institute Falknerstrasse 9, CH-4051 Basel, Switzerland gemlab@ssef.ch You are invited to contribute to the newsletter with short articles of interest for other SSEF Alumni members. All contributions should be sent to Dr. Michael S. Krzemnicki mkrzemnicki@bluewin.ch and will be published after editing if appropriate for this newsletter. SSEF Alumni Newsletter No. 9 info@ssef-alumni.org