World of Magnificent Spinels Provenance and Identification

Online release pages 1-2, 269-282 No.11 January 2012 (Updated May 2015) World of Magnificent Spinels Provenance and Identification Burma Vietnam Cornflower-Blue Spinel over 10ct from Vietnam Inclusions in Spinel Introduction WORLD OF MAGNIFICENT SPINEL: PROVENANCE AND IDENTIFICATION Adolf Peretti (1) Anong Kanpraphai-Peretti (2) and Detlef Günther (3) (1) GRS Gemresearch Swisslab AG, Sempacherstr. 1, CH-6003 Lucerne, Switzerland (2) Anong Kranpaphai-Peretti, GRS (Thailand) Co LTD, JTC Building, Silom 19, Bangrak, Bangkok 10500 (Thailand) (3) Laboratory of Inorganic Chemistry, ETH Hönggerberg, HCI, G113, CH-8093 Zurich, Switzerland INTRODUCTION The ancient gemstone spinel has experienced an enormous shift in popularity over the last decade. For centuries, the transparent stone was coveted by royalty, especially when found in large sizes like the famous ‘Samarian Spinel’ from the Iranian Crown Jewels, considered to be the largest of its kind at 500 carats. Several pieces of the British Crown Jewels include vivid red spinels, such as the famous ‘Black Prince’s Ruby’, which were erroneously named because there were no scientific methods for separating similarly coloured gemstones at the time of their discovery. Spinel may have also occurred in deposits where ruby was found, further complicating its identification in earlier times. Attributes of its value Like any precious stone, there are traits it needs to sustain its appeal. Beauty, rarity and durability of the stone are key factors, but colour is also critical for its Fig. 1 Magnificent cornflower blue Vietnamese Cobalt wide acceptance. Fortunately, spinel occurs in a variety spinel over 10 carats in size. This type of colour is of colours besides the red favoured by royalty. Spinel is considered to be the most expensive. ©Yavorskyy, Bangkok one of very few gemstones that are found in a vast restored. Spinel by contrast has remained free of such Price hike array of colours, such as blue (ranging from greyish- vibrant pinkish-red spinel from Namya. Similarly disgrace since it has not yet been subject to similar blue to cornflower blue), reds (from vibrant pinkish-red striking colours have also surfaced in the Mansin covert and widespread treatment. Recently, The rise in popularity of spinel is of course reflected in to vivid red), oranges and all kinds of fancy colours. mines located in the Mogok valley. Beside the vivid red co-diffusion and heat-treatment has appeared in its price surge as shown in the chart above. In the last Besides its rainbow of colours, another winning feature spinel varieties, the attractive pinkish-reds received spinel but fortunately it can be easily detected. five to ten years, spinel prices have increased more of spinel is that it can be found in large sizes, often the highest prices for spinel around the world. Along- than 10-fold depending on its colour and origin. Today, combined with good clarity. With a hardness rating of 8 side the more recently discovered deposits, the classi- Impact of JADE Act spinel prices are comparable to those of unheated on the Mohs scale, spinel is a very durable material. cal and historically known spinel mining sites in the sapphire; this is particularly true with cornflower blue Gem-quality spinel, often found in the same deposits Pamir mountains of Tajikistan have resumed produc- Before the new generation of African ruby was discov- spinel from Vietnam or vivid red spinel from Mogok, alongside ruby or sapphire, is a very rare occurrence tion, unearthing important large stones over 40 carats ered in Tanzania (Winza) and Mozambique, spinel Burma (Myanmar) and vibrant red spinel from today. in size. However, not all spinels are recovered from was considered a highly desired alternative to the ever Mahenge, Tanzania. mountainous mining sites. Spinel are also found in increasingly rare ruby emerging from the classical The principal attribute of spinel’s surprising discovery Regions determine colour ancient river sites known as alluvial deposits in Tanza- Burmese (Myanmar) origins. Back in 2008, the ban on to the gemmological world is its immense variability by nia, Vietnam, Madagascar, Sri Lanka and Burma Burmese ruby, called the ‘Tom Lantos Block Burmese colour and geographic traits particular to specific Geology plays an important role in the location where (Myanmar). Primary marble deposits in Burma JADE (Junta's Anti-Democratic Efforts) Act of 2008’, regions. This is an enormous help to researchers in certain colours of spinel are found. The most sought- (Myanmar), Vietnam and Tanzania as well as olivine banned all importation of Burmese ruby and jade into separating spinel by origin and identifying treatments after colours in spinel are vivid red and cornflower blue. veins within marble deposits in Tajikistan are also a the US in protest of human rights violations occurring in the microscope. The vivid red varieties are found principally in the source of spinel. in that country. With that embargo in place, the interna- Mogok Valley in Burma (Myanmar). On the other hand, tional gem- trade scrambled to fill the demand for the cornflower blue material derives mainly from Undisclosed enhancements top-quality ruby by looking for close alternatives like Vietnam, but it can also be found in Sri Lanka and fine spinel. This refocus actually provided a big pay-off Tanzania. This blue variety has become known in the Corundum (ruby and sapphire) had to deal with a shat- in bringing interesting new colours to the fore espe- trade as Cobalt Spinel. tering blow in recent years upon revelations of non- cially where couture high-jewellery was concerned. disclosed product enhancements such as beryllium In the last decade, the discovery of spinel deposits in treatment, lead-glass treatment, high-temperature Vietnam, Tanzania and northern Burma’s (Myanmar) treatment with fissure healing and the resurgence of Namya region took the gem world by surprise with the conventional diffusion-treatments. This has resulted in production of incredibly beautiful colours such as the a loss of consumer confidence that has yet to be fully 01 Introduction INTRODUCTION The ancient gemstone spinel has experienced an enormous shift in popularity over the last decade. For Fig. 2 A set of three faceted Sri Lankan spinels centuries, the transparent stone was coveted by ranging from 12 to 16 carats in size. A typical colour royalty, especially when found in large sizes like the variety of this origin is the pastel purple to violet famous ‘Samarian Spinel’ from the Iranian Crown ‘lavender’ colours. © Yavorskyy, Bangkok Jewels, considered to be the largest of its kind at 500 carats. Several pieces of the British Crown Jewels include vivid red spinels, such as the famous ‘Black Prince’s Ruby’, which were erroneously named because there were no scientific methods for separating similarly coloured gemstones at the time of their discovery. Spinel may have also occurred in deposits where ruby was found, further complicating its identification in earlier times. Attributes of its value Like any precious stone, there are traits it needs to Fig. Sp3a Fig. Sp3b sustain its appeal. Beauty, rarity and durability of the stone are key factors, but colour is also critical for its Fig. 3a-b (Left) A tray of faceted Burmese spinel at the gem market in Mogok. (Right) Vietnamese spinel with wide acceptance. Fortunately, spinel occurs in a variety star effect formed by inclusions of silk arranged in three different directions. © GRS Gemresearch Swisslab of colours besides the red favoured by royalty. Spinel is one of very few gemstones that are found in a vast restored. Spinel by contrast has remained free of such Price hike array of colours, such as blue (ranging from greyish- vibrant pinkish-red spinel from Namya. Similarly disgrace since it has not yet been subject to similar blue to cornflower blue), reds (from vibrant pinkish-red striking colours have also surfaced in the Mansin covert and widespread treatment. Recently, The rise in popularity of spinel is of course reflected in to vivid red), oranges and all kinds of fancy colours. mines located in the Mogok valley. Beside the vivid red co-diffusion and heat-treatment has appeared in its price surge as shown in the chart above. In the last Besides its rainbow of colours, another winning feature spinel varieties, the attractive pinkish-reds received spinel but fortunately it can be easily detected. five to ten years, spinel prices have increased more of spinel is that it can be found in large sizes, often the highest prices for spinel around the world. Along- than 10-fold depending on its colour and origin. Today, combined with good clarity. With a hardness rating of 8 side the more recently discovered deposits, the classi- Impact of JADE Act spinel prices are comparable to those of unheated on the Mohs scale, spinel is a very durable material. cal and historically known spinel mining sites in the sapphire; this is particularly true with cornflower blue Gem-quality spinel, often found in the same deposits Pamir mountains of Tajikistan have resumed produc- Before the new generation of African ruby was discov- spinel from Vietnam or vivid red spinel from Mogok, alongside ruby or sapphire, is a very rare occurrence tion, unearthing important large stones over 40 carats ered in Tanzania (Winza) and Mozambique, spinel Burma (Myanmar) and vibrant red spinel from today. in size. However, not all spinels are recovered from was considered a highly desired alternative to the ever Mahenge, Tanzania. mountainous mining sites. Spinel are also found in increasingly rare ruby emerging from the classical The principal attribute of spinel’s surprising discovery Regions determine colour ancient river sites known as alluvial deposits in Tanza- Burmese (Myanmar) origins. Back in 2008, the ban on to the gemmological world is its immense variability by nia, Vietnam, Madagascar, Sri Lanka and Burma Burmese ruby, called the ‘Tom Lantos Block Burmese colour and geographic traits particular to specific Geology plays an important role in the location where (Myanmar).

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