Identification of Sapphires from Madagascar with Inclusion Features Resembling Those of Sapphires from Kashmir (India)

Identification of sapphires from Madagascar with inclusion features resembling those of sapphires from Kashmir (India)

Dr. Adolf Peretti (FGG, FGA) and Francesca Peretti (GG)

In late 2016, a new sapphire-producing mine was dis- covered at Bemainty, near Ambatondrazaka and Didy in Madagascar (Figure 5). The mine produced a consider- able amount of large sapphires, including Padparadascha and yellow sapphires (Figures 4a, c). The mining area has now been closed. The Bemainty mine lies north of the Didy mine (Figure 5) in a slightly different geological setting within a so-called Imorona-Itsindro Series. The formation of sapphire at the Didy mine is believed to be related to Nb-Ta pegmatites that are mapped in the area south of Didy. Niobite inclusions found within sapphires from Didy suggest a connection to these pegmatites (Peretti and Hahn, 2013). The geology of the new Bemain- ty mine and its surrounding does not indicate such Nb-Ta pegmatites, yet niobite inclusions in one of the samples Figure 1a Figure 1b from the new mine have been found. Currently fieldwork Figures 1a, b. Mining in the Bemainty area near Ambatondrazaka the area is not being undertaken due to elevated security in Madagascar before April 2017. Figure 1a shows a soil profile risks (Figures 1a, b). Spectacular inclusion features have been found in sap- of theheavily weathered rocks containing sapphires. Fig. 1b gives phires from Bemainty and they resemble textbook Kash- an idea of the large crowd at this illegal mining site, with several mir (India) sapphire inclusions (Figures 6 to 11). As a con- tens of thousands of miners participating, leaving a trail of de- sequence, a certain degree of misinterpretation of these struction in the protected rainforest. (Photo is from the miner) sapphires seems to exist in the market, and a series of stones from Madagascar has possibly been falsely classi- fied as Kashmir sapphires (Krzemnicki 2013). Kashmir sapphires have seen an unprecedented rise in value with prices that can reach well over $100,000 per carat, while their counterparts from Madagascar are ten times less expen- sive. This offers a great potential for fraud and the correct significant amounts of sapphire besides isolated single find- identification is thus an important part of the challenge of ings. Madagascar is the major sapphire producer dominat- internationally recognized gem-testing laboratories. ing the world market supply. Madagascan sapphires are In order to distinguish the sapphires from the new mine in occasionally misrepresented as originating from Myanmar, Madagascar from those from Kashmir, we have prepared Sri Lanka or Kashmir. InColor/ICA Figure 1a Figure 1b in the a Master Set of more than 50 reference samples from both Bangkok market, all reported of being from the new depos- mines, carefully selected to cover the entire range of inclu- it. Among the samples are more than two dozen sapphires sion features (Figures 4a, b, c). that contain typical Kashmir inclusions (e.g. Figure 6). These types of inclusions were found in rough samples that we The GRS Kashmir-Ambatondrazaka Master Set obtained directly from the mine and kept as rough, Sizes The Kashmir Master Set of was prepared from the GRS range from 2 to 10 carats. Approximately 20% of our a very reference collection, comprised of hundreds of sapphire particular and unique way (Peretti et al, 1990). In the high reference samples from Kashmir, collected over the last 20 Himalayas, pegmatites intruded into a series of amphibo- years. Many of those samples have been cut in our own lite and ultramafic rocks (Figure 3b). During that process, facility and then categorized according to different inclu- the pegmatite was depleted of silica and a reaction rim sions features, covering all the literature-published features of tourmaline was formed around the pegmatites (Peretti of Kashmir sapphires. et al, 1990). The Ambatondrazaka Master Set includes samples that This process has become known as de-silification and we received from two commissioned independent agents it ultimately leads to the formation of sapphires within the that we have sent to the new mines, as well as cut and pol- pegmatites. The sapphires either formed within the peg- ished stones from more than five different reliable sources matite or in the reaction zone. There are different types of Figure 2. Countries with sapphire deposits of commercial sapphires with varying inclusions such as tourmaline, pla- importance. The Kashmir sapphire mine in northern India gioclase and amphibole, depending on the spot where has been exhausted for decades and does not produce the sapphire was formed. o o o o o o 30 0 30 60 90 o 60 UNITED 60 KINGDOM DENMARK RUSSIAN FEDERATION NETHERLANDS BELARUS GERMANY POLAND BELGIUM CZEC. H REP UKRAINE AUSTRIA MONGOLIA FRANCESWITZERLAND ROMANIA ITALY BULGARIA KYRGYZSTAN Figure 2. Countries with sapphire deposits of commercial impor- PORTUGAL SPAIN GREECE TURKEY tance. The Kashmir sapphire mine in northern India has been SYRIAN TAJIKISTAN TUNISIA CYPRUS Jammu and exhausted for decades and does not produce significant amounts ARAB REP IRAN AFGHANISTAN Kashmir CHINA MOROCCO LEBANON IRAQ of sapphire besides isolated single findings. Madagascar is the o ISRAEL JORDAN o KUWAIT PAKISTAN 30 ALGERIA LIBYAN ARAB NEPAL major30 sapphire producer dominating the world market supply. Western BAHRAIN JAMAHIRIYA EGYPT QATAR Sahara SAUDI VIETNAMadagascanM sapphires are occasionally misrepresented as origi- ARABIA UNITED ARAB INDIA EMIRATES nating from Myanmar, Sri Lanka or Kashmir. MAURITANIA LAO OMAN MALI NIGER BURMA SENEGAL CHAD YEMEN THAILAND BURKINA SUDAN MYANMAR GAMBIA FASO CAMBODIA Formation of Kashmir Sapphires GUINEA BENINNIGERIA SIERRA LEONE GHANA CENTRAL ETHIOPIA 1 1 ultramafic rocks (enstatite-olivine) LIBERIA AFRICAN R.EP 2 3 4 MALAYSIA 2 chromium-anthophyllite-tremolite CAMEROON SOMALIA SRI LANKA UGANDA SINGAPORE o CÔTE CONGO o 3 garnet-amphibolite 0 D'IVOIRE GABON KENYA 0 4 amphibolite D.R. CONGO INDONESIA 5a 5b 6 5 alteration zone TANZANIA a) talc-cabonate b) biotite ANGOLA 6 contact zone, tourmaline rim ZAMBIA 7b (dravite, schorl) corundum-plagioclase-pegmatite ZIMBABWE 1 7 a) unaltered rock NAMIBIA MOZAMBIQUE b) partially prelaced into BOTSWANA MADAGASCAR fine-grained mica, kaolinite and carbonate corundum (colorless) or o SOUTH o 7a sapphire (light blue or blue) 30 AFRICA 30 1 m Below: Figure 3a. The Kashmir sapphire deposit is an isolated Figure 3b. The geology of the formation of Kashmir sapphire at spot at an elevation of 4600 meters within the Himalayan moun- this primary deposit. A pegmatite intrudes rocks of peridotite tain range. One of the authors (Adolf Peretti) studies the primary and amphibolite and produces a tourmaline reaction zone (Per- 30 o 0 o deposit30 o at the site in the early60 o1990s. Only a few gemologists90 o in etti et al, 1990). the world made it to the Kashmir sapphire mine. (Photo: Rainer Kündig). Figure 4a. Parts of the GRS reference collection with sapphires from the new deposit near Bemainty in Madagascar

Figure 4b. the GRS Kashmir reference Master Set. Figure 4c. A selection of padparadscha sapphires in a lot from the new mine in Mada- gascar for the GRS reference collection.

Below: Legend for Figure 5, opposite page. Legend

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48°30’E� 48°40’E � 48°50’E M v e r y f i n e streamers blue color zoning

white, cloud-like inclusions, assorted with emerging small rutile

irregular clouds of pin points over a wide area with isolated few rutile needles

leathers

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Figure 6. Inclusion features found in a high-value sapphire over Figure 7. Sketch of the Madagascar sapphire inclusion details 10 cts, originating from the new Bemainty sapphire mine in Mad- (Figure 6) revealing subtle differences to similar inclusions found agascar as seen under 60x magnification and oblique fiber optic in sapphires from Kashmir (Figures 15 and 17), e.g. development illumination. The minuscule details resembling clouds, streamers of small rutile needles around clouds. This phenomenon is absent and striae, possess all the hallmarks of Kashmir sapphires. Only in Kashmir sapphires. the study of minute details reveals differences (Figure 7). (Photo: Matthias Alessandri)

Figure 8. Oscillating color zoning in a sapphire from the new mine in Madagascar. Note the occasional appearance of yellow color zoning. Such color zones have not been found in Kashmir sapphires of the GRS Master Set.

Figure 9. Fluid feathers containing yellow infillings. This is due to the late hydrothermal alteration and weathering process found in sapphires from Madagascar. This alteration within fluid inclusion feathers is absent in Kashmir sapphires. (Photo: Willy Bieri)

Figure 10. Clusters of long zircons included in the sapphires from Madagascar. The zircons have extensive tension cracks and are often corroded and milky. They are distinctly different from the zircon inclusions found in Kashmir sapphires (Figure 16). Figure 11. Oscillating milky and blue zones and streamers perpendicular to the growth zones are found in this gemquality cornflower blue sapphire from the new mine in Madagascar (viewed under fiber optic illumination). At first glance, it resem- bles the inclusion features of a Kashmir sapphire. Only the study of minor details allows a distinction from features observed as inclusions in Kashmir sapphires.

Figure 12a. Two examples of Kashmir sapphires that are part of the GRS Kashmir reference Master Set. On the left is a crosssection through a 20-ct gem-quality Kashmir sapphire with a polished window. On the right is a 100+ ct Kashmir sapphire carving by Glenn Lehrer, California. The carved Kashmir contains a 5-mm dravite tourmaline over- growth, proving its Kashmiri origin. All the samples were obtained before the opening of the new deposit in Mad- agascar.

Figure 12b. The same two Kashmir sapphires as in Figure 12a are exposed to long-wave ultraviolet light and exhibit distinctive fluorescence. Left: Core of a Kashmir sapphire shows yellow-orange fluorescence, followed by a zone of inert reaction to UV-light and an outer rim of red fluorescence. Right: The Kashmir sapphire shows red fluorescence throughout its body and possesses a distinctive zone of intense red fluorescence, restricted to a growth zone within the crystal. Yellow fluorescence was exclusively found in Kashmir sapphires, while red fluorescence can also be observed in sapphires from the new deposit in Madagascar. Figure 13 Figure 14

Figure 15 Figure 17

Figure 16 Figure 18 Preliminary Comparison Study Implications for the Market We have compared the following properties of the The surfacing of new gemstone deposits is proving to samples for this preliminary report: be a serious challenge for gemological laboratories. A solution to this problem is to have a reference collection A) Solid inclusions that has been established over a period of more than 20 B) Fluid inclusions years. It took us some time to collect the different types of C) Age of zircon inclusions Kashmir sapphires with different inclusion properties. Only D) Color zoning two to three Kashmir sapphire samples per year could be E) Inclusion features indicative of Kashmir sapphires purchased from reliable sources between 1994 and 2015. F) UV-fluorescence analysis Finding reference samples of the new mine from Mad- agascar was especially difficult, since traders did not co- Further analysis is currently focused on oxygen iso- operate in selling samples to the laboratory, particularly topes, zircon ages, LA-ICP-MS analysis and SEM-EDS. We those with Kashmir-like inclusion features. It was necessary will report further on our findings in the near future. For the for us to get the samples in 2016 anonymously, pretending first report, we focused on sapphires that are potentially to be serious buyers through agents and paying high mar- at risk for being mixed up with Kashmir sapphires. We have ket prices. found the following results. Based on our Master Sets, we can confirm that com- A) Zircon habit: both origins may contain long zircon paring the minute details of the sapphires makes it possi- crystals (Figures 10, 16). They can, however, be easily dis- ble to distinguish the two different origins. Re-checking is tinguished from each other. Uraninite crystals are only recommended for sapphires in the market between 2016 present in Kashmir sapphires. Tourmaline inclusions of dra- and 2017, which are claimed to be from Kashmir. vite compositions are exclusive to Kashmir sapphires as of now (Figure 14). Warning About Potential Origin-Misinterpreta- B) Kashmir sapphires contain a special type of pseudo tion of Padparadscha Sapphires from the Be- secondary fluid inclusion features. These types of inclusions are largely absent in our master stones from the new mainty Deposit deposit in Madagascar (Figure 15). Remarkably large and beautiful padparadscha sap- C) Isolated yellow color zones were found in samples phires have been found in this new deposit with sizes that from the new mine in Madagascar (Figure 8). These yellow can exceed 20 carats. We came across cases where they color zones are not present in Kashmir sapphires. have been misinterpreted in the trade as originating from D) The age of Kashmir sapphire zircons was found to be Sri Lanka. 23 million years old. The sapphires from the new deposit in The padparadscha from Bemainty can be identified Madagascar are older than 200 million years as can be based on their characteristic color zoning (Figure 19) in concluded from the geological set-up of the rock forma- combination with their distinctive FTIR spectrum (Figure tions. This can be established using LA-ICP-MS analysis. 20). The FTIR spectrum though is not exclusive to this origin. E) Al-hydroxide inclusion features, often referred to We have encountered situations where clients con- as Kashmir-type inclusions, show small differences. These firmed a padparadscha’s origin as from this new depos- differences can be seen, if the inclusion features are it in Madagascar, but declined to accept our gemstone sketched and analyzed in detail (example Figure 7). report since the stone came with other gemstone reports F) Fluorescence analysis has shown that UV-fluores- stating a Sri Lankan origin ass the most probable prove- cence criteria reported earlier (Krzemnicki 2013) cannot nance. This requires a “Trade Alert” to the public in addi- be applied (Figures 12a, b). tion to the that previously published about the new Kash- mir-like sapphires from Madagascar

Figure 13. An amphibole inclusion in a Kashmir sapphire is accompanied by a fluid inclusion feather. The singly isolated fluid inclusion voids are arranged in a distinct flat area. When illuminated with an oblique fiber optic light, the fluid inclusion tubes reflect simultane- ously. This type of fluid incisions is typically found in Kashmir sapphires. Figure 14. Opaque cubic inclusions found in Kashmir sapphires, identified as uraninite. They are generally absent in sapphires from the new deposit in Madagascar, but can be found in sapphires from Adranondambo in southern Madagascar (Gübelin and Peretti, 1997, 1998). For the purpose of distinguishing sapphires from Kashmir from sapphires from the new deposit in Madagascar, these crystals are helpful, although not always present, but serve as an important distinction criteria. Figures 15 and 17. Clouds of Al-hydroxide are often found in gem-quality Kashmir sapphires. These inclusions were generally believed to be exclusive to Kashmir sapphires until the arrival of sapphires from the new sapphire mines in Madagascar. Figure 16. A cluster of long needle-shaped zircons without any tension cracks, found in a sapphire from Kashmir. The inventory of zircon habits is relatively complex and includes various types of different zircon inclusions. Comparing zircon habits, corrosion features, growth zoning inside the zircons and geometry of the tension cracks around zircons provides a key feature for distinguishing the Mad- agascan sapphires from their Kashmir counterparts. Figure 18. Dravite inclusions in a sapphire from Kashmir are still considered a strong indication for their origin (see their occurrence at the primary deposit, Figure 3b). Further inclusion analysis in sapphire from the new deposit is currently underway to test this argu- ment. Figure 19. Microphotograph taken of the interior structure of a padparadscha sapphire (over 20 cts in size) from the new mine in Madagascar. Pink, yellow and orange color zoning is revealed with occasional isolated blue zones that are not shown in this picture (40x microscope magnification using transmitted light). These features, in combination with the infrared spectrum (Figure 20) as well as additional chemical and spectroscopic data, are characteristic of padparadscha sapphires from this new deposit. This allows the determination of the origin of this new type of padparadscha sapphire from the Bemainty deposit near Ambatondrazaka.

Fig. 20 FTIR-transmission spectra of an unheated Padparadscha sapphire from the new mine in Madagascar (Bemainty, Ambatondrazaka). Note the prominent line at 3160 cm-1. Similar spectra were described for rubies from Winza, Tanzania (Peretti 2008).

References

1) E.J. Gübelin and Adolf Peretti, 1997. Sapphires from the Adranondambo mine in SE Madagascar: evidence for %T metasomatic skarn formation. Journal of Gemology, 25,7, pp. 453-516.

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