Geographical Overview of

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1 Ruby Geographical Overview of By K.T. Ramchandran, FGA Silvia Sequeira, FGA Gemmological Institute of India (GII), Mumbai Rough crystal of Burma ruby. 80 solitaire INTERNATIONAL february 2014

2 Tech Talk Ruby belongs to the noble corundum family. The word corundum is derived from the Sanskrit word kurand or kuruvinda. Ruby, derived from the Latin word ruber (red), represents the embodiment of the most beautiful red colour conceivable in the universe. However, the finest and most precious shade is known as Pigeon Blood Red. The late Dr. Edward Gubelin, a renowned gemmologist, described ruby as red magic and its colour as a drop of the heart s blood of Mother Earth. Ruby is considered to be the most powerful gem in the galaxy of gemstones; especially in the Indian context, among the Navgraha gemstones, ruby occupies the centre of the planetary position, representing the Sun. Robert Webster, in his famous book Gems: Their Sources, Descriptions and Identification described the myth and magic of ruby as, The high esteem placed on ruby is further indicated by the names applied to it in Sanskrit. These were ratnaraj, which means king of precious stones and ratnayaka means leader of precious stones. In India people described the glowing hue of the ruby as an inextinguishable fire which burns within the stone and asserted that this inner fire could not be hidden and would shine through the clothing or any material wrapped around the stone. Ruby was said to preserve the health of the wearer, for it removed evil thoughts. Rubies and other red stones whose colour suggests blood were thought to be a remedy for haemorrhage and inflammatory diseases. The Burmese believed that it was not sufficient to simply wear the stones, they must be inserted into the flesh and become part of the wearer s body. Doing this was thought to give protection against wounds of various kinds. Chemical Composition The mineral corundum is a crystallised form of aluminium oxide (Al 2 O 3 ) with traces of impurities modifying the water-white colour of the pure mineral. Colour It is a most difficult thing for a layman to believe that ruby, with its intense red colour, is the same material belonging to the corundum family, which in its pure form is a perfectly colourless material. Colours of rubies vary in all shades of red to a deep crimson. The colour intensity is substantially influenced by the chromium percentage. If the oxidation condition of the chromium changes, the orange coloured shade occurs. Other shades such as red, brown red or purple red can be ascribed to traces of iron and vanadium, respectively. Increased proportion of iron causes a brownish tint. Important Geographical Locations Myanmar (Burma) The most famous locality for fine rubies is the district around Mogok in upper Myanmar. The Mogok Stone Tract is an area of some 1,000 km. In the late 19th century a mining company was incorporated in London by the name of Burma Ruby Mines Co. No underground mining was involved in the early stages and up to 1908 the company was doing well. After the economic depression, emergence of Vernuil synthetics and the First World War, the company suffered heavily and in 1925 it closed down. After the failure of the company, mining in Burma reverted to native methods. Pit mining and cutting holes into the hillside were used for mining in those days. The Mogok mines were nationalised in The government runs several mines in the Mogok area. Basalt, marble, metamorphic rock as well as pegmatites were all involved in the crystallisation of ruby. Mogok rubies are the classic examples of this type of formation. In this case, the mother rock is white, partially dolomite limestone marble. It is a most difficult thing for a layman to believe that ruby, with its intense red colour, is the same material belonging to the corundum family, which in its pure form is a perfectly colourless material. Colours of rubies vary in all shades of red to a deep crimson. solitaire INTERNATIONAL february

3 This is the common mode of occurrence for ruby from Myanmar. At Mogok, ruby occurs in a metamorphosed limestone, traces of which provide calcite and apatite inclusions in the host crystals. Both primary and secondary deposits are mined in the Mogok area. Ruby in such primary deposits are mainly hosted in white marble along with other meta sediments of the Mogok metamorphic belt. The corundum bearing marbles are always in contact with other mica-rich granite gneiss. The most common crystalline inclusions from Mogok are calcite, spinel, apatite, rutile and zircon crystals (with or without haloes). Dark brown to opaque slabs or plates of phlogopite mica are also seen. The most diagnostic inclusions of Mogok ruby is the dense white clouds of rutile which are termed as silk. They are short, intersecting in three directions at angles of 60 or 120 degrees. These are also responsible for the asterism or star effect in ruby. Mogok rubies also display inclusion of boehmite (dislocation) needle. Along with solid crystal inclusions rubies from Mogok also contain negative crystals of primary origin. Negative crystals can often be recognised by their high relief due to the liquid or gas filling, creating two phase-like inclusions. Untreated rubies from Mogok contain far fewer secondary liquid (fingerprintlike) inclusions compared to rubies from Thailand, Cambodia, Sri Lanka or Kenya. Crystals in Burma ruby. Burma gem area map. Ruby has been found at other localities in Myanmar including the Sagyin Hills near Mandalay and Nanyaseik near Mainglon. The notable purple coloured rubies from Mong Hsu, 250 km east of Mandalay, are heavily fractured and the purple colour needs to be removed by heat treatment. The deposit was discovered in Silk-like inclusions. 82 solitaire INTERNATIONAL february 2014

4 Tech Talk Thailand and Cambodia Thailand (Siam) and Cambodia are very important sources for rubies. The ruby deposits occur along the Thai/Cambodia border in the Chanthaburi and Trat provinces in Thailand, and neighbouring Battambang province in Cambodia. The rubies originate from identical deposits, thus the internal features of rubies from Thailand and Cambodia are identical. Siam rubies are generally brownish red and somewhat dark in colour. Rubies are found in a wide area including Bo Ram, Nong Bon, Bo Waen and Tok Prom in Thailand and Pailin in Cambodia. The centre for the gem trade in this area is the Thai town of Chanthaburi. Boehmite needle inclusions. All gem deposits in this area are derived from iron-rich basalt. The large amount of iron content of the mother rock makes the Siam rubies darker. The stones are found in coarse yellow or brown sand, overlaying a bed of clay or basaltic rock. Mining is by simple methods. Siam rubies. Thai rubies are characterised by a complete lack of rutile silk and other exsolved mineral particles in the basal plane. Thai rubies have long white needles (boehmite) parallel to the edges of rhombohedron faces at the junction of polysynthetic twinning planes. According to Gubelin, they consist of tubes filled with a colourless transparent liquid, along dislocation and pressure parting lines. Other features include liquid inclusions of both primary and secondary origin, the latter being present in almost every specimen. Colour zoning is rarely seen in Thai rubies, which may have solid crystal inclusion of almandine garnets, apatite, pyrrhotite, plagioclase feldspar, olivine or diopside. Thai rubies have both primary and secondary liquid inclusions in abundance. Thai ruby inclusions. Thailand (Siam) and Cambodia are very important sources for rubies. The ruby deposits occur along the Thai/Cambodia border in the Chanthaburi and Trat provinces in Thailand, and neighbouring Battambang province in Cambodia. The rubies originate from identical deposits, thus the internal features of rubies from Thailand and Cambodia are identical. solitaire INTERNATIONAL february

5 India is known for ruby deposits. In the state of Karnataka, the world famous Mysore rubies are found in abundance. Vietnam During the last years, Vietnam has become a major ruby producer. Vietnam rubies in many aspects are striking in their similarity to those from Myanmar, as the geology of the two areas is similar. Some rubies were found to contain distinct medium dark to dark blue colour zoning. Rubies from Luc Yen area are usually less saturated than those from Quy Chan. Rubies coming from this area range from purplish red to purplish pink. Luc Yen rubies show an angular parallel growth pattern, but the short rutile needles seen in Burmese rubies are not observed in samples studied at GII. The commonest mineral inclusions in Luc Yen and Quy Chau rubies are calcite, dolomite, rutile, diaspore and phlogopite. All red and pink samples from Quy Chau and Luc Yen appeared red under long and short wave U.V. light. Some of the Vietnam rubies also show the Trapiche effect reported by Gubelin in Mong Hsu rubies. famous for ruby deposits. In Andhra Pradesh, rubies are found in Hindpur, Anandpur, Kalyandurg, Dharmavarum and Khammam District. The states of Madhya Pradesh and Chhattisgarh are also famous for ruby deposits. In the state of Orissa, places like Bolangir, Jilander, Kalahandi and Sambalpur are well-known for ruby deposits. Rubies are also found in Kerala s Wyanad district. Indian ruby are mostly opaque having good asterism. Transparent variety is also found in Orissa, Chhattisgarh and Tamil Nadu. Indian ruby cut stones. Vietnam ruby map. India India is known for ruby deposits. In the state of Karnataka, the world famous Mysore rubies are found in abundance. Areas such as Chennapatnam, Mysore and Coorg in the southern part of Karnataka and Alipur near Bangalore are famous for rubies. In the state of Tamil Nadu, Kayalpatnam, Kankayan and Karur are Pakistan The ruby deposits occur in metamorphosed recrystallised dolomite marble in a narrow belt extending from the Hunza valley to Ishkoman, a distance of more than 100 km. Crystals are well formed and range from pink to a fine red. Other mineral inclusions were dolomite, the potassium mica phlogopite, which occurs as reddish brown flakes and featherlike greenish crystals of the calcium mica. Pyrite, pyrrhotite and apatite were also found. However, no trace of rutile has yet been reported, so no Pakistan star rubies are likely to occur (so far). Afghanistan The Jegdalek ruby deposits are in the southern portion of the Sorobi district, 60 km south-east of Kabul in the Jegdalek river valley. Gem ruby is found in situ in interstratified Proterozoic marble and gneisses intruded by granitic. The ruby- 84 solitaire INTERNATIONAL february 2014

6 Tech Talk bearing marble is notably coarse-grained. In terms of colour, they resemble most of the gems of Burma and Sri Lanka. consist of irregular distorted shingles which are opaque and black and slightly golden in colour. Colour zoning in Jagdalek rubies is very sharp and narrow and forms in a typical hexagonal pattern parallel to the c axis. Occasionally clouds of minute exsolved particles are found. Rough ruby crystals. The most distinctive features of Jagdalek rubies are the small spots or zones of sapphire blue colour. A sharp division between red body colour and the blue patch is highly characteristic of Jegdalek rubies. Crystals, apparently of calcite, are common. Other plate-like inclusions Blue colour zone. PROPERTIES OF RUBY Crystalline inclusions. Species - Corundum Variety - Ruby Chemical Composition - Al2O3 (Aluminium Oxide) Colour - Medium light to dark red, purplish red, orangish red Crystal System - Trigonal Habit - Prismatic Transparency - Transparent to opaque Lustre - Vitreous Hardness - 9 Pleochroism - Dichroic (strong to weak) Specific Gravity to 4.00 Spectrum ,4750,4765,5500,6592, 6680,6928,6935,6942 A Cleavage - 4 directions parting & lamellar twinning Fracture - Conchoidal to uneven Optic Sign - Uniaxial Negative Refractive Index Birefringence to Dispersion UV Light - inert-strong Indian Name - Manik Afghanistan gem area map. The Jegdalek ruby deposits are in the southern portion of the Sorobi district, 60 km south-east of Kabul in the Jegdalek river valley. Gem ruby is found in situ in interstratified Proterozoic marble and gneisses intruded by granitic. The ruby-bearing marble is notably coarsegrained. In terms of colour, they resemble most of the gems of Burma and Sri Lanka. solitaire INTERNATIONAL february

7 Tajikistan gem area map. Tajikistan Ruby mines are located north-west of the village of Urgab in western Tajikistan near the China border. The Republic of Tajikistan is a mountainous landlocked country in central Asia. It borders Afghanistan in the south, Uzbekistan in the west, Kyrgyzstan to the north, and China to the east. Pakistan is separated by the narrow Wakhan corridor in the south. Tajikistan ruby inclusions. Sri Lanka Corundum with a wide range of colours is found in south-west Sri Lanka. Sri Lankan ruby inclines to pink rather than crimson but the stones are very bright and lively. Mining is simple and any method of reaching the illam (gem gravels, perhaps 15 m down) is used. Sri Lankan rubies Sri Lanka gem area map. Long and short needles. 86 solitaire INTERNATIONAL february 2014

8 Tech Talk show inclusions distinctive enough for the location to be determined. They are noted for many types of liquid inclusions like fingerprints, feathers, web- and mesh-like patterns. Flakes of biotite are very characteristic and rutile needles are generally longer and more slender than those seen in Myanmar stones. Polysynthetic twinning is somewhat rare in Sri Lankan rubies as compared to other sources. Strong colour zoning and solid inclusions of zircon with helo, mica and apatite are characteristic. Healing fissure is very common in Sri Lanka rubies, these inclusions occur in every shape, size and pattern. The vast majority of Sri Lankan ruby crystals are unevenly coloured with large areas devoid of colour altogether. Liquid inclusion. Feathers and lamellar twinning. Zircon helo inclusions in Sri Lankan ruby. Kenya In 1973, American geologists Tim Miller and John Saul discovered ruby in Tsavo West National Park, in the Mangari area. Facet grade crystals were much less. Most of the rubies are heavily included, suitable only for cabochons, and must be heated to improve the appearance. Rutile silk is not found in Kenyan rubies but may contain concentrations of minute exsolved particles. Colour zoning is common and large numbers of fingerprints and feathers are the hallmark of Kenyan rubies. Solid inclusions are less common in Kenyan rubies. Overall, the internal appearance of rubies from Kenya is characterised by large numbers of liquid inclusions bounded and criss-crossed by rhombohedral twin lamellae and boehmite needles. Kenya ruby. Colour zoning is common and large numbers of fingerprints and feathers are the hallmark of Kenyan rubies. solitaire INTERNATIONAL february

9 Tanzania gem area map. It is said that the best quality Winza rubies are so clean and so colourful that it is very difficult to differentiate them from the synthetics. Inclusions in these material show bent fibbers with polycrystalline filling of probably secondary minerals. Twin lamellae-like straight lines are seen. Tanzania Of greater importance are the varieties of sapphire and rubies from the Umba river valley in north-eastern Tanzania, near the Kenya border where sapphires are mined from several pits in and around a greyish green serpentine pipe. Rubies from Morogoro area of Tanzania are of good colour and inclusions are similar to some found in Myanmar ruby. Clouds of rutile crystals and coarse rutile octahedral inclusions with slightly rounded solid material (spinel) or negative crystals, were found. Zircon, apatite and pyrope have also been identified. The potential for asterism has been found in some specimens. The mines are situated in the western Uluguru Mountains. Winza It is said that the best quality Winza rubies are so clean and so colourful that it is very difficult to differentiate them from the synthetics. Inclusions in these material show bent fibbers with polycrystalline filling of probably secondary minerals. Twin lamellae-like straight lines are seen. Winza rubies. Winza mine. 88 solitaire INTERNATIONAL february 2014

10 Tech Talk Mozambique (Niassa National Reserve) Niassa is a huge reserve located in north Mozambique along the Ruvuma River and the Tanzanian border. In 2008, rubies were discovered inside the Niassa Reserve during a hunting operation located in the bush more than 30 km from the nearest village of M sawize. In Northern Mozambique, the ruby rush at Niassa and Montepuez was probably a direct consequence of this interest for Winza rubies. With these three new ruby deposits producing many good stones, the ruby trade has started to look at East Africa as a possible alternative to Burma. (Right) Madagascar gem mining area map. (Below) The Gondwanaland super continent. Needle-like inclusions. Zircon crystals. Fine silk in needle form. Mozambique rubies. Madagascar Madagascar is an island located off the south-east coast of Africa. Geologically it is believed that some millions of years ago, Madagascar s landmass was separated from the super continent of Gondwanaland. Madagascar is blessed with many gem minerals especially ruby and sapphires. A large portion of the Madagascar rubies have been heat-treated to enhance its colour. Ruby in Madagascar is found in the area called Vatomandry located in the centraleastern side. Vatomandry rubies are said to be good quality material. Another area where ruby mining is done is Andilamena in northern-central Madagascar. These rubies are said to be comparatively lower in quality. References: Gemstones by Edward Gubelin Gems: Their Sources, Descriptions and Identification by Robert Webster InColor magazine by ICA Ruby & Sapphire by Richard W. Hughes Gems & Gemmology by GIA Internal World of Gemstones by Edward Gubelin Photoatlas by E.J. Gubelin & J.I. Koivula Gemstone Properties by K.T. Ramchandran & J. Panjikar R & D Department, Gemmological Institute of India solitaire INTERNATIONAL february