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Corundum Asia

Posted by Olav Revheim  
Corundum Asia
January 23, 2012 09:12PM
    
This Article is Under Construction


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Can you help make this a better article? What good localities have we missed? Can you supply pictures of better specimens than those we show here? Can you give us more and better information about the specimens from these localities? Can you supply better geological or historical information on these localities?

Corundum is a common and attractive mineral that are or has been mined as a gemstone or as an industrial product at various localities around the world. The corundum article is therefore split into a multiple articles, one for each continent as follows:

Corundum main article
Corundum Africa
Corundum Americas
Corundum Asia
Corundum Australia
Corundum Europe and Russia

As of now, only the Corundum Americas has reached the "the first draft" level.

Corundum var.ruby
Afghanistan
Kabol Province (Kabul Province), Surobi District (Sorobi District), Jegdalek (Jagdalek; Jagdalak; Jagdalik) ruby deposit

Corundum crystals up to 1,1 cm © Dan & Diana Weinrich Minerals
,

Corundum 2,1 cm crystal© Dan & Diana Weinrich Minerals
Corundum 3 cm crystal © Rob Lavinsky


Corundum 1,7 cm crystal © Rob Lavinsky
Corundum 2,5in tall specimen© Rob Lavinsky


Corundum 1,6 cm crystal © Rob Lavinsky
Corundum 3 cm crystal © Rob Lavinsky

The first confirmed mining operations near Jegdalek is the production of marble for the Taj Mahal in 1637. The overland transportation of the marble blocks from Jegdalek to through some of the most rugged and inhospitable landscapes on the planet is a truly remarkable feat. Today Jegdalek is one of the more accessible Afghan gem deposits, being just east of the Jagdalek village and not far from the Kabul-Jalalabad highway. The nearness to the capital has caused some friction between the central government and the people of the two mining villages. As a result, the mining has been rather infrequent the last few years.

It is not known when the mining operations for ruby started, but it may have been as early as the 14th century. When the first European visited the mines in 1879, the following was reported:

“In the year 1879 the so-called ruby mines of the late Amir of Afghanistan, Shir Ali, which are situated near the village of Jagdalak in Kabul, were visited by Major Stewart of the Guides. Two specimens of stones, called yakut by the natives, and samples of the matrix, were forwarded to the office of the Geological Survey for examination. The stones proved to be spinel, and the matrix a crystalline micaceous limestone. Major Stewart states that the Amir kept a strict guard over the mines and only allowed particular friends of his own to work them.”

The identification as spinel was wrong and it was evident already at that time that the ruby mining had been going on for a long time, despite the failure of earlier European visitors in the 1830-ties to report on the mining.

The ruby found at Jegdalek is normally of pinkish, red or violet colors. According to Bowersox (2000) only 15% of the production qualifies as rubies as defined by the gem industry. The remainder of the production is considered as pink sapphire (75%) and violet to blue sapphire (10%). Some of the crystals show color zoning. The best quality gem rubies rival those of Burma in terms of color and quality. Mineral collectors would also classify the pink sapphires as ruby.

The corundum here is most often found as subhedral, translucent crystals and/or crystal groups up to 3 cm. The largest single crystal reported by Bowersox(2000) weighed 174 carats. Facet grade material are rare and top quality stones rarely exceed 5 carats, although larger faceted stones of good quality up to 32 carats are known. Well-formed euhedral crystals not suitable for facetting are collected by the miners and sold as mineral specimens, as they are more valuable as mineral specimens than cabochon roughs. Individual crystals up to minimum 5 cm are known. The best mineral specimens ( large well developed crystals as an aesthetic matrix specimen) may well reach prices exceeding USD 10,000. It should still be possible to find a reference specimen for less than 50 USD.

Well-developed crystals are more common for the smaller crystals. Bowersox et al. (2000) gives a thorough description of crystal shapes, trace element analysis, list of inclusions and occurances as well as a comparative analysis between the Jegdalek corundum and similar occurances. ,

The rubies are found in narrow beds near calc-silicate horizons in a wedge shaped marble body of significant size ( 500 to 2000m wide and 4 km long). The marble units are oriented parallel to main regional foliation developed during the Himalayan orogeny. For the ruby bearing horizons near Jegdalek, this means nearly vertical. The rubies are excavated from long, narrow trenches of up to 60m depth, following the ruby-bearing horizons. These trenches are easily visible in the barren mountain slopes, and it is believed that only a fraction of the total rubies in place are mined.

The marble is predominantly a calcite-marble and the rubies are found in two distinctly mineral assemblages:
1) Ruby+mica+feldspar+/-graphite+/-tourmaline+/-titanite+/-pyrite
2) Ruby + spinel+/-chlorite+/-phlogopite+/-titanite+/-pyrite

The marble units consist of metamorphosed platform carbonates, that where originally inter-bedded with clays and organic material. The ruby bearing marbles are underlain by a Precambrian(?) metamorphic basement and intruded by Oligocene plutonic units. The marble itself contains sufficient Al and Cr for Cr bearing corundum to form, and evidence suggests that the corundum is formed in a closed system within the marble during retrograde metamorphic conditions in amphibolite facies (620 < T < 670 °C and 2.6 < P < 3.3 kbar) during the Himalayan orogeny (24,7 +/-0,3 mill MA). It is believed that F and Cl from evaporites assisted the mobilization of Al from clays.

Literature:

Gary W. Bowersox, Eugene E. Foord, Brendan M. Laurs, James E. Shigley, Christopher P. Smith (2000): Ruby and Sapphire from Jegdalek, Afghanistan, Gems and Gemology, Vol 36, No 2 pp 110-126

Gary W. Bowersox, Bonita E. Chamberlin(1995). Gemstones of Afghanistan. Geoscience Press

Richard Hughes: The rubies and spinels of Afghanistan- a brief history. www.ruby-sapphire.com

Vincent Pardieu: (2010): Blog Title: GIA_FE17_Afghanistan, fieldgemology.org

Vincent Pardieu and Guillaume Soubiraa (2006/2008): From Kashmir to Pamir, Summer 2006: Gemological expedition report to ruby, emerald and spinel mining areas in Central Asia. Part 2: Afghanistan: Land of beautiful gems and unique people. Fieldgemology.org

Virginie Garnier, Gaston Giuliani, Daniel Ohnenstetter, Anthony E. Fallick, Jean Dubessy, David Banks, Hoàng Quang Vinh, Thérèse Lhomme, Henri Maluski, Arnaud Pêcher, Kausar Allah Bakhsh, Pham Van Long, Phan Trong Trinh and DietmarSchwarz (2008): Marble-hosted ruby deposits from Central and Southeast Asia: Towards a new genetic model, Ore Geology Reviews 34 (2008) 169–191

Sibley International Corp. (2007): ASSESSMENT OF AFGHANISTAN GEMSTONE INDUSTRY. AFGHANISTAN SMALL AND MEDIUM ENTERPRISE DEVELOPMENT PROJECT , UNITED STATED AGENCY FOR INTERNATIONAL DEVELOPMENT

Corundum
Burma (Myanmar)
Mandalay Division, Pyin-Oo-Lwin District, Mogok Township

Corundum 14 mm crystal© 2003 John H. Betts
Corundum 22mm FOV© 2005 M. Kampf
Corundum 1,7 cm crystal© Rob Lavinsky


Corundum 14 mm crystal© Rob Lavinsky
Corundum 3,4 cm specimen© fabreminerals.com

Corundum 3,5 cm crystal© Rob Lavinsky
Corundum 4,0 cm specimen© Joseph A. Freilich


Corundum 3 cm crystal©
Corundum 3,9 cm specimen© Rob Lavinsky

Corundum
2,3 cm crystal
© Dan & Diana Weinrich Minerals
Corundum
2,5 cm crystal
©

Corundum 3,4 cm crystal© Weinrich Minerals, Inc.
Corundum 2,1 cm crystal© Dan & Diana Weinrich Minerals

Mogok is considered the unrivalled source of high quality rubies and is also a producer of nice sapphires. Rubies have been mined there since before recorded history. Mogok’s standing compared to other ruby producing are visualized by the following quote from the USGS 2008 ruby production and resource overviews:

“The average values per carat of the imports were Thailand $20, India $4, Hong Kong $34, Switzerland $459, and Germany $50. The average value per carat of imports from Burma was $331.”

The roots of ruby mining in Mogok is shed in myth and lore, as is the case for many classic gem localities .Although not entirely in line with modern geological theory, the following myth quoted from Sally Dickingson DeLeon (derived from G.F. Kunz quoting Taw Sein Ko) has a nice ring to it:

“The Valley of Rubies was created in ancient times when Naga (a serpent) laid three eggs: out of the first hatched the King of Pagan (the major region in ancient Burma), out of the second hatched the emperor of China, and the third egg was stolen away by a hunter but he accidentally dropped it in a stream. The third egg cracked and released all of the precious rubies that spread throughout the land (of Myanmar’s modern day stone tract.)”

Finding the true history is in many cases just as hard as finding the gems in the first place, and the following account from Martin Ehrmann should probably also be considered a myth, although it has a more historically correct tone:

Modern Mogok was founded in 579 A.D., when it was all jungles and thick forests. While hunting in the jungles, headhunters of the Sab Bwa of Momeik lost their way and slept under a tree. At daybreak, they heard birds singing and hovering over them. Investigating the commotion of the birds, they ran into a mountain break full of beautiful rubies. They collected as many as they could carry and brought them to the Sab Bwa of Momeik. He immediately realized the wealth of the area and sent some of his household to establish Mogok. It was first called Thahpainpin (Pomegranate) for the fruit growing abundantly there, and such a little village still exists on the extreme west limits of Mogok.”

What is certain is that Mogok eventually became the private property of and operated by the Burmese king. Hughes (xxxxxx) the final takeover happened in 1597, when the Burmese monarch, Nuha-Thura Maha Dhama-Yaza annexed the district, exchanging a small piece of his territory to the hapless Shan saopha (prince), who was powerless to stop him. The Burmese kings operated the mines as their own wallet, paying little attention to the needs of the workers and villagers in the mining districts, except the merciless treatment of those stealing produce from the mines.

The British established the “The Burma Ruby Mines, Ltd “in 1889. Despite a large initial interest from investors, the company never became a commercial success and the company was mainly dormant from 1925 until handing back its mining license in 1931. The failure of making commercial success is generally considered to be due to poor geological investigation and the high cost of establishing the infrastructure required for modern mining operations. It has also been voiced the opinion that the DeBeers’ representative in the Board was more concerned with establishing DeBeers provided diamonds as the girl’s best friend than supporting steps that would lead to successful ruby mining in Mogok.

In the period between the end of “The Burma Ruby Mines Ltd.” and the nationalization of the mining by the military junta in the 1960-ties was dominated by small scale mining by primitive means. After 1969 all ruby mining was, in theory, controlled by the government, but despite the risk of fierce punishment, most of the production was illegally smuggled to the gem markets in Thailand. It appears that the government of Burma is easing up somewhat on its control of the country, and that private gem mining again are possible to a certain degree.

It is more than anything the color and longevity of production that has made the best Mogok rubies famous. The vast majority of the stones are cut as gems, simply because the gem value is far greater than the specimen value. It is difficult to estimate how large the production has been from Mogok, both historical and present time, and it is also impossible to know how large good ruby crystals can get from there. Both Palagems and the USGS has aimed to estimate production the last couple of decades, but none of them differentiates between Mong Hsu and Mogok rubies. The USGS estimates for production between 1995 and 2005 varies between a low of 6kg in 1995 and 1476kg in 1998. Estimating an average value of 331USD/carat will add up to a significant amount of money (although it should be noted that the finest stones will yield several thousand USD/ct even in their natural state).

The ruby crystals are typically stubby consisting of prism/pyramids terminated by pinacoid faces and modified by the rhombohedron. Crystals often display appear irregular due to alterations between pinacoid and rhombohedron forms.

“Many larger rubies have almost a skeletal appearance which is more consistent with a metasomatic growth/corrosion than high-grade metamorphic growth. A number of small ruby crystals have a coating of blue and colorless davyne, followed by mizzonite and/or nepheline, then phlogopite ± pargasite and diopside before reaching marble facies. These indicate the importance of fluids in the formation of the rubies” (Harlow)

The Mogok ruby mining has undoubtedly yielded several large crystals, and it is impossible to estimate how large these crystals may have been. The 196-ct Hixon Ruby of the Los Angeles County Museum of Natural History is one of the finest Burmese ruby crystals on public display, and any crystal exceeding 2 cm should be considered a good crystal from the area

The color range from light pink, through bright red, to deep garnet-red. Most tend to be slightly purplish-red in hue position, and grade into purple and violet sapphires.

Even though Mogok is mostly known for rubies, sapphire can also be found here, although from a slightly different geological environment. Most of the sapphires are dull and black and their quality cannot, on a general basis, be compared with the rubies. The crystals may be nice though, well-formed double pyramids up to 25-30cm are known, and occasionally also gem quality blue, yellow, orangy yellow, orangy, purple crystals are known. It appears that the largest corundum gems from Mogok is more frequently large sapphires than rubies.

- Still lacks paragenesis, petrology and geology


Corundum
Burma (Myanmar)
Mandalay Division, Pyin-Oo-Lwin District, Mogok Township, Chaunggyi

Corundum 4,4 cm specimen© Rob Lavinsky


Corundum
Burma (Myanmar)
Mandalay Division, Pyin-Oo-Lwin District, Mogok Township, Dattaw Hill

Corundum 3,8 cm crystal© Rob Lavinsky




Corundum
Burma (Myanmar)
Mandalay Division, Pyin-Oo-Lwin District, Mogok Township, Nampai Valley

Corundum 21mm crystal© Keith F Compton



Corundum
Burma (Myanmar)
Mandalay Division, Pyin-Oo-Lwin District, Singu Township, Letpanhla, Marla

Corundum 3,3 cm specimen© Nuno Miguel Santos




Corundum
Burma (Myanmar)
Shan State, Loilem District (Loilen District), Möng Hsu (Monghsu; Maing Hsu)

Corundum 1 cm crystal© Jasun McAvoy



Corundum
China
Hebei Province, Baoding Prefecture, Fuping Co.

Corundum 2 cm crystal© Jiangbin


Corundum occurs in a Al-rich gneiss belonging to the precambrian (~2,5 Ga) Wanzi stratified rock series with sillimanite, garnet and gedrite.

Literature:

Liu Shuwen and Liang Haihua(1997): Metamorphism of Al Rich Gneisses in Taihang Mountain Archean Metamorphic Complex, abstract,


Corundum
India
Jammu and Kashmir

Corundum on tourmaline, Scale at the bottom is 1 in. ©


The Kashmir sapphires are of the kind creating legends. Not only is the gem mine in one of the most remote and difficult accessible areas of the world, but the finest gems found here are of an unrivalled size and show an intense blue color. In addition, the current whereabouts of the unique collection gathered by the Kashmiri maharajah is not known.

The discovery of the location is surrounded by myth, and several versions has been told. It is however clear that the first stones appeared on the market in Simla in 1882 and that the first stones was sold at “ridiculously low prices”. The Maharajah of Kashmir was however quick to intervene and gained control of the mining site and the gem trade. In the early years the sapphire was abundant and large volumes of stones and money exchanged hands:
“….gave an extremely good output of very large stones from about the year 1881 to about 1887. This is a historical fact and is well known to many living people. A few specimens of sapphire then collected are still preserved, jealously guarded by the State, in the toshakhana [treasury], and have been seen by the writer. Of these there is at least one large piece, bigger than a polo or croquet ball, and others smaller all of a rich blue colour. There are also many cases of cut gems of pendant size which are superficially as large as florins” (C.S. Middlemiss, 1931, quoted from Richard W. Hughes (xxxxxx)).

The original source was soon depleted, and in 1887 the Maharajah asked the Geological Survey of India for assistance in mapping the location and to discovery additional reserves. Tom D. LaTouche, the Survey’s deputy superintendent visited the mines and gave an outstanding report on the locality, geology, the occurance of corundum and the mining techniques. His report is published in full on palagems.com.

Since then, mining has been sporadic, and professional mining has only been carried on a few years at the time. Even though large quantities of corundum has been mined, (> 100kgs/yr in periods) the gem production has not been anything near the glorious first years that made the reputation of Kashmir sapphires.

The Sapphire mining area are still today very remote and only accessible by helicopter or by 4-6 days strenuous trekking from Kishtwar on a narrow mule track. The mining area itself lies in a small valley at an altitude of 4600m, and consist of a “series of irregular openings, pits, and alluvial workings on and just below a sharp ridge” ( RICHARD V. GAINES (1946)). Although almost 70 years of legal and illegal mining has taken place since Gaines’ visit to the mines, the general appearance of the mining area probably remains the same.

LaTouche gives a describes the rocks in the mining area in detail. The main rock is a micaous gneiss interbedded with carbonate rocks and small bands and pods of a light green amphibole-bearing rock. These metasedimentary rocks are traversed by numerous granite pegmatite dikes carrying tourmaline, cyanite, euklas and small garnets as accessory rocks. Some of the visitors to the mines reports vugs in the pegmatites, displaying beautiful crystals of quartz and tourmaline. These has remained untouched, probably due to a combination of the long and tiresom transport of the retrieved material and the potentially much greater value of the sapphire crystals.

The original find of corundum crystals up to 5 in long and 3 in.wide was in a fine grained plagioclase in a pegmatite. Most of the corundums has however been washed out from the debris on the valley floor, often with a white clay on the surface. The intense “Kashmir blue” color is rare, and only 1% of the corundum found are of gem quality, although this figure may have been as high as 25% in the early days. Corundum occurs both as non-crystalline black or opaque white masses and as well developed hexagonal crystals. The crystals are normally not of uniform color and the color can range from colorless, white ( both transparent and opaque), all grades of blue from a very light blue to almost black, pinkish purple and black opaque. The most attractive blue color are amazing, but often as a thin layer on the outside of light colored crystals. As the crystals are often severely pitted on the exterior, the blue color can be just small patches of blue on a whitish crystal.

Auctioned, top quality gems has achieved prices exceeding 130.000 USD/ carat or more than half a million for a gram. Representative uncut crystals can be reasonably priced ( less than 100 USD).

Literature:

Richard W. Hughes (1997): Ruby & Sapphire

Richard V. Gaines (1946): The Kashmir sapphire mines, The Himalayan Journal 13

Dr. A.M. Heron(1930): The gem-stones of the Himalya, The Himalayan Journal 2

Tom D. La Touche (1890): The sapphire mines of Kashmir, palagems.com reprinted from Records of the geological survey of India Vol 23, pt2, pp 59-69.

Ed Cleveland, www.kashmirblue.com


Corundum
India
Karnataka, Mysore District

Corundum 10,5 cm specimen © G. van der Veldt

Corundum
1,6 cm crystal
© Rob Lavinsky
Corundum 1,5 cm crystal © Knut Eldjarn

Corundum 3 cm crystal. © Russell G. Rizzo
Corundum 5,1 cm specimen © Rob Lavinsky




Corundum
India
Karnataka, Dakshina Kannada ( South Kanara, South Canara) district, Subramanya (Subrahmanya, Subramanium)


Corundum 5,5 cm crystal. © 2001 John H. Betts
Corundum 3 cm specimen © 2001 John H. Betts



Corundum
Nepal
Bagmati Zone, Dhading District, Chumar Mines (Chhumar Mines)

Corundum , 5,7 cm crystal© Rob Lavinsky


Corundum , 4.1 x 3.2 x 2.1 cm specimen© Rob Lavinsky
Corundum , 5 cm tall © Rob Lavinsky

The original find of corundum in the Chumar mine was made by a group of American explorerers(F. John Barlow, Allan Bassett, and Charles Key) in the early 1980-ties. They did not bring many specimens with them, but the location is still being worked today although limited and sporadic because of their isolated locations, high altitudes, and harsh seasonal weather conditions.

The Chumar mines are located on the southeastern flank of the Gamesh Himal, just below the Main Central Thrust (See Stöcklin J for more detailed discussion) in the metasedimentary Nawakot series. The ruby deposits occure with phologopite, muscovite, scapolite, margarite,
spinel, titanite, pyrite and graphite in marble lenses 60-150 m wide and 1 km long. The ruby occurs in bands (up 3-4 cm wide) parallel with the foliation of the marble.

The ruby crystals are most often elongated pyramids, but rather dull, opaque and not very sharp. The color is often pinkish, but bicolored pink/blue crystals are known. The individual crystals may reach 5cm or more, and crystal clusters exceeding 10cm in size are known.

Literature:

William Heierman,www.corunduminium.com

Virginie Garnier, Gaston Giuliani, Daniel Ohnenstetter, Anthony E. Fallick, Jean Dubessy, David Banks, Hoàng Quang Vinh, Thérèse Lhomme, Henri Maluski, Arnaud Pêcher, Kausar Allah Bakhsh, Pham Van Long, Phan Trong Trinh and DietmarSchwarz (2008): Marble-hosted ruby deposits from Central and Southeast Asia: Towards a new genetic model, Ore Geology Reviews 34 (2008) 169–191


Christopher P. Smith, Edward J. Gublein, Allen M. Bassett, Mache N. Manandhar (1997): Rubies and Fancy-Color Sapphires from Nepal, Gems & Gemology, Volume 33, Number 1


Corundum
Nepal
Mechi Zone, Taplejung District,

Corundum 50mm specimen© Oleg Lopatkin
Corundum 65 mm specimen© Oleg Lopatkin

Blue corundum occurs in a gneiss matrix. The locality is poorly described.


Corundum
Pakistan
Azad Kashmir, Muzaffarabad district, Neelum Valley, Nangimali (Nangimali Top; Lower Khora marble deposits)


Corundum 5,7 mm crystal© Chinellato Matteo
Corundum 1,2 cm© Weinrich Minerals, Inc.


The Nangimali ruby occurrence was discovered in 1988, and the first stones appeared on the market in the 1990-ties and marketed as Kashmir ruby. This should not be confused with the famous sapphire locality in Indian Kashmir. The Nangimali rubies are mined from several small mines ( as pr. 2006: Chitakata, Khora, Lower Cora and Nangimali top) located from 2900 to 4600m above sea level. At the highest altitude, mining can only take place 3-4 months a year due to the harsh weather conditions. The maining is operated by the state owned "Azad Kashmir Mineral Industrial Development Corporation", and in 2006, some 50 miners where active. ( after Pardieu 2006).

The ruby occurs in a metasedimentary sequence with amphibolites, mica schists and marbles ( the Nangimali formation) which forms a large syncline that surfaces both near the valley floor (2800m ) and higher up (4600m). The rubies follow two different marbles, one fine grained yellowish, and a coarser grained grey marble. The thickness of the ruby bearing zones varies from 10-30cm some places to 3-6m at the mining sites. Rubies are enriched in 0,5-2cm thick veinlets in shear zones within these zones.

The rubies are most often found as scalenohedral crystals up to 5 cm long with sections up to 1 cm in width. The colour of ruby varies from pink to pinkish red to deep red. Peˆcher et. al. (2002) gives an annual production in a 1990-1994 test period to be 69 kg of rough ruby pr/year, with a yield of 11g/ton. Pardieu (2006) does not provide detailed production figures, but productions does not seem significantly different from the test mining.

Literature:

Vincent Pardieu and Guillaume Soubiraa(2006) From Kashmir to Pamir, Summer 2006: Gemmological expedition report to Ruby, Emerald and Spinel mining areas in Central Asia, Field trip report published on www.fieldgemology.org

Virginie Garnier, Gaston Giuliani, Daniel Ohnenstetter, Anthony E. Fallick, Jean Dubessy, David Banks, Hoàng Quang Vinh, Thérèse Lhomme, Henri Maluski, Arnaud Pêcher, Kausar Allah Bakhsh, Pham Van Long, Phan Trong Trinh and DietmarSchwarz (2008): Marble-hosted ruby deposits from Central and Southeast Asia: Towards a new genetic model, Ore Geology Reviews 34 (2008) 169–191

A. Peˆchera, G. Giuliani, V. Garnier, H. Maluski, A.B. Kausar, R.H. Malik, H.R. Muntaz (2002):Geology, geochemistry and Ar–Ar geochronology of the Nangimali ruby deposit, Nanga Parbat Himalaya (Azad Kashmir, Pakistan), Journal of Asian Earth Sciences vol. 21 pp 265–282


Corundum
Pakistan
Gilgit-Baltistan (Northern Areas), Gilgit District, Hunza Valley


Corundum 2,7 cm crystal© Jose Zendrera
1,6 cm crystal© Dan & Diana Weinrich Minerals

Corundum 1,1 cm crystal© Jose Zendrera
Corundum 2,94 cm specimen© Aymeric

Corundum 5,4 cm specimen© Edwards Minerals


Ruby deposits in the Hunza Valley lies next to the main Karakoum highway between Pakistan and China, and Garnier et.al (2008) suggests that the deposits was discovered in the early 80-ties during construction of this road, but Reman et.al(2009) refers to an earlier project report from 1975 (Farooqi) on Hunza rubies. Clanin(2008) also refers to test production and reserve estimates done in the early and mid 1970-ties by the Pakistan Mineral Development Corporation. Based on the test production, they conclude that the producing marble deposit is 2,100–3,000 meters thick and extends 25 km on strike. There are ruby workings scattered across the deposits. These reports show a rather optimistic potential for commercial development, but similar occurrences as far away as Bisil in the Bisha valley, more than 100km west for the Hunza valley show there is a potential for large ruby resources in the area. The rugged and difficult terrain, poor infrastructure and probably also unclear regulatory environment adds to the complexity, and mining is sporadic and small scale.

The corundum occurs in an impure marble in the Baltit formation. The Baltit formation is a sequence of the Karakoum metamorphic complex, which lies north of the main Karakorum thrust. It is a meta-sedimentary unit that can be traced from the Afghanistan Border to the Indian Border.

The corundum bearing marbles once was carbonate rocks on the continental shelf of the Eocene Thety’s ocean before being metamorphosed during the Himalayan orogeny. The rocks of the Hunza deposits are believed to have been methamorphosed at 2,5kbar and 600-650 degC forming corundum associated with phlogopite, muscovite, scapolite, margarite, spinel, titanite, pyrite, amphiboles and graphite. These marbles contains sufficient amounts of Al and Cr (and V) to allow red corundum to form whithout any hydrothermal or metasomatic influx of elements.

The corundum found in the Hunza vally is pink, various hues of red, grading towards purple and lilac. They are embedded in calcite and may form nice crystals. A variety of crystal forms are known. Their maximum size is difficult to estimate, but it appears that the individual crystals rarely exceeds 2-2,5 cm.

Literature:

Virginie Garnier, Gaston Giuliani, Daniel Ohnenstetter, Anthony E. Fallick, Jean Dubessy, David Banks, Hoàng Quang Vinh, Thérèse Lhomme, Henri Maluski, Arnaud Pêcher, Kausar Allah Bakhsh, Pham Van Long, Phan Trong Trinh and Dietmar Schwarz (2008): Marble-hosted ruby deposits from Central and Southeast Asia: Towards a new genetic model, Ore Geology Reviews 34 (2008) 169–191

Jim Clanin(2008): Gemstone and mineral mining in Pakistan’s mountains, In Color, spring issue.

Abdul Rehman, Muhammad Alam, Babar Khan (2009): Mineral Resources of Central Karakuram National Park & Suggested Safe Mining Techniques. WWF Pakistan, report


Corundum
Sri Lanka


Corundum FOV 19mm© 2005 M. Kampf
Corundum 8mm© 2010 Michael C. Roarke

1cm © Dan & Diana Weinrich Minerals
Corundum ca 4cm crystal© 2007 Peter Cristofono

Corundum 2,9 cm crystal© J.Scovil
Corundum 2,8 cm crystal© J.Scovil

For centuries, the island of Sri Lanka has been a key source for a variety of gemstones, including corundum. Sri Lankan gems were mined, set into jewelry, and traded abroad since 500 B.C., if not before. Ancient Greek and Chinese historians referred to the beautiful gems of Sri Lanka, and King Solomon is supposed to have wooed the Queen of Sheba with Sri Lankan precious stones. The Indians called Sri Lanka “Ratnadeepa,” which means “Island of Gems.”

.Marco Polo wrote of his visit in 1292: “I want you to understand that the island of Ceylon is, for its size, the finest island in the world, and from its streams come rubies, sapphires, topazes, amethyst and garnet.” It is predominantly in the area around the city of Ratnapura (Singhalese for ‘gem town’) these gems are extracted. The exact locality of any corundum specimen found in the vicinity of Ratnapura is often unknown. The mining operations are also often (always?) of a very temporary nature.

Marco Polo was right in that most of the gems, including corundum, found in Sri Lanka originally were washed from streams, Today corundum is retrieved from a gem bearing gravel, the illam, which is generally a 0.1-1.5m thick horizon up to 30m below surface level.

Most Sri Lankan corundum is found as hexagonal bi-pyramidal shapes, and can vary appreciably in form and habit. The crystals are often water-worn to lesser or bigger degree. Crystal groups are rare, as is crystal more than 2-3 cm. The crystals suitable for cutting will normally end up in rings and pendants and not in thumbnail boxes in mineral collections. This is also the case for the bigger crystals, and most of the large sapphires among the crown jewels of monarchies, and museums around the world are of Sri Lankan origin. Several of the bigger ones, those approaching 500ct (100g), have their own names, such as the 423 carat Logan Blue Sapphire, the 563 carat Star of India, and the 478 carat Queen Marie of Romania's Sapphire. A 400ct cut sapphire is roughly equivalent with a 35*30*20mm large stone. The original crystals for these large cut stones must have been significantly larger.

The classic sapphire colour is blue, and a significant portion of the corundum is various hues of blue. The best colored crystals approach the silky blue of the Kashmir sapphires, but the full range from a pale sky blue to black crystals can be found. There is some evidence that the colour of the sapphires varies from region to region in Sri Lanka. In particular blue sapphires from Rambuka and Mattara have distinctive colorations unmatched elsewhere on the island. The colour and clarity of some sapphires can be enhanced by heat treatment and polishing. In fact only 8-10 % of the corundum mined in Sri Lanka is of high gem quality not requiring any further heat treatment or processing to enhance colour.

Other notable varieties of sapphire from Sri Lanka are coloured yellow and orange, the former called "pusparga" and the latter "ratnapusparga". The colour in this case is controlled mainly by iron with minor chromium. Yellow sapphires are widespread but some of the best examples have been recorded from the area around Aluthnuwara in the Balangoda. Another variety is known as "pathmaraga"or” padparacha”. It shows a range of yellow-orange-pink-red colours, particularly as flashes within the stone, depending on its orientation. It is said that the padparacha variety ideally shall contain both the warm gold of a tropical sunset and the cold pink of a lotus flower. Although the language in this description is somewhat more poetic than one would normally expect when describing a mineral variety, it certainly holds some merit.

Sapphires of other colours, most notably greens, browns and purples also occur but are not common.

Sri Lanka also produces some ruby although there is some controversy as to their true status. Some authors argue that Sri Lankan rubies should really be classed as pink sapphires. Sri Lankan rubies are generally much lighter red colour than the rubies of Burma, and the majority of gem quality stones being various shades of pink with a slight purple tinge.

A significant boost for the Sri Lankan gem industry was provided by the discovery of "geuda" corundum through the involvement of Thai gem dealers in the late 1970's. Geuda is a translucent to opaque variety of corundum with a milky, greasy or smoky appearance in reflected and transmitted light and some stones show a silky lustre. It has little value of its own accord until it is heat treated during which the different varieties of geuda can take on a whole range of colours, depending upon trace constituents within them, and also undergo significant improvements in their clarity, transparency and lustre. In essence, worthless waste material can be converted into high value, gem-grade coloured sapphire by heating if it is suitable. The heating process, in its simplest form, dissolves the mineral micro-inclusions, usually rutile, back into the structure of the corundum.. Its discovery has had a significant effect in enhancing the economic viability of many small gem-mining operations, which, until then, had been solely dependent upon gem quality coloured corundum to sustain them.

All of these small scale mining operations are processing the illam gravel. There is considerable variation in the thickness, extent and composition of the illam, the later of which has appears to have some correlation with the gem content of the gravels. In some areas the illam is shallow (<3m below the surface), thin (ca. 10-20 cm), generally characterised by quartzose gravels and blue grey clay and is laterally impersistant, presumably occupying depressions in the underlying bedrock surface. At other sites it is several tens of meters (20-30m) below the surface, 0.5-1.5 m thick and laterally extensive (several 100 m2) and is occasionally repeated, with several illam horizons encountered as the shaft or pit is dug. This type of occurrence may represent a buried river valley or flood plain. Generally there is no way to predict multiple bands unless there has been earlier mining in the same area.

There is no direct correlation between thickness of the illam and corundum content . The thinnest illam can give significant yield whilst the thickest can be barren. In terms of bulk mineralogical composition of the illam, there is a broad range from clay dominated to those containing fine-grained sand. The former are generally blue- green-grey in colour and have a high clay content whilst the sandier illams are dark greens, brown and black. Both are often associated with high contents of organic material which releases a pungent odour when the illam is excavated and in fact presents some difficulties when extracting the illam from deeper, poorly ventilated shafts and pits. The illam is normally capped above and below by blue-green coloured clay.


Corundum
Sri Lanka

Central Province

Corundum 8mm specimen© Joseph A. Freilich


Corundum
Sri Lanka
Sabaragamuwa Province, Ratnapura District, Ratnapura, Gem gravels


Corundum ca 6cm crystals© Peter Slootweg


Corundum ca 1,8cm crystals© Rob Lavinsky


Corundum crystals up to 1,5 cm© Rob Lavinsky


Corundum ca 1,4in crystals© Joseph A. Freilich


Corundum 2,8 cm crystal© Weinrich Minerals, Inc.
Corundum 3,49 ct.© Chinellato Matteo

Corundum 11mm crystal© Michael C. Roarke
Corundum 1,8cm crystal© Stefan Koch

Corundum 4,3cm crystal© Rob Lavinsky
Corundum 2,7cm crystal© Dan & Diana Weinrich Minerals

Corundum 13mm crystal© Kristalle and Crys
Corundum 62mm crystal© Oleg Lopatkin

Corundum 2,6cm crystal© Rob Lavinsky
Corundum 1,6cm crystal© Rob Lavinsky
.
Corundum 3,2cm crystal© Rob Lavinsky

Corundum 3,2cm crystal© Weinrich Minerals, Inc.
Corundum 3,5cm crystal© Weinrich Minerals, Inc.

Corundum 3,4cm© Dan & Diana Weinrich Minerals
Corundum 23mm crystal©




Corundum
Sri Lanka
Uva Province, Badulla District


Corundum up to 3 cm crystal©

Corundum 2,9 cm crystal© J.Scovil
Corundum 2,8 cm crystal© J.Scovil



Corundum
Sri Lanka
Uva Province, Badulla District, Badulla, Passara Gem Mine


Corundum 3 cm crystal© Rob Lavinsky
Corundum 1,3 cm crystal© Rob Lavinsky
.
Corundum 2,5 cm © Edwards Minerals



Corundum
Sri Lanka
Uva Province, Moneragala District, Wellawaya, Galbkka


Corundum 2,3 cm crystal© Rob Lavinsky

Corundum
Thailand
Chanthaburi Province


Corundum almost 10cm©


"In ancient times, Chanthaburi had no gems. Suddenly during a dark night, villagers saw a light glittering in the sky and then watched it drop in the area of Khao Ploi Waen. People ran after the light and saw green rays coming out of a hole and there, they found mae ploi (the mother of gems) and started worshipping the rock. When they tried to touch it, however, the mae ploi flew away and following her were louk ploi or baby gems. Thousand or tens of thousands of louk ploi escaped with her and those that could not follow scattered around the area of Chanthaburi."

The first written account of sapphires from Chantaburi is from the Chinese traveler Ma Huan from 1408. John Crawfurd, British envoy to Siam and Cochin China (1828) provides a quite detailed account:

"The only gems which are ascertained to be minerals of Siam, are the sapphire, the Oriental ruby, and the Oriental topaz [yellow sapphire]. These are all found in the hills of Chan-ta-bun [Chanthaburi], about the latitude of 12 degrees, and on the eastern side of the Gulf. The gems, from what we could learn, are obtained by digging up the alluvial soil at the bottom of the hills, and washing it. The gravel obtained after this operation is brought to the capital for examination. Both the ruby and sapphire of Siam are greatly inferior in quality to those of Ava [former capital of Burma]. Several specimens were shown to us during our stay, but none of them of any value. The mines of Chan-ta-bun, not with-standing this, are a rigidly guarded monopoly on the part of the King."

Richard Hughes gives a vivid account of the mining history of Chantaburi, from the early 15th hundred and even today some mining takes place, but the resources are close to depleated. Chantaburi now are more known as a trade centre for colored gems from all over the world.

Corundum is associated with mostly weathered alkaline basalts of Cenozoic age, and are found both in eluvial and alluvial gravels. The gem bearing layers are normally between 0,3 and 1m thick. As the corundum are found at, or near the it's oigin, the crystals should not be weathered. Traditionally, there has been two main mining areas in the Chantaburi province, all of them with numerous pits and diggings. Near Chantaburi town, Khao Ploi Waen and Bang Kha Cha areas has produced blue, green and yellow sapphires, as well as black star sapphire, whereas the localities in the vicinity of mountain has produced both rubies and blue sapphires.

It is difficult to say how large or how well formedd the crystals could get here, as not many crystals has been saved from cutting throughout the many centuries of mining. The pictured crystal is probably one of the largest.

Thailand has through the centuries produced gem corundum from several areass also outside Chantaburi and the neighbouting Trat province. These are also mostly depleted and does not play any significant role today, neither as gem nor specimen producers. For those interested, the literature references are both good and interesting reading.

Literature:

Richard W. Hughes (last update 2011): Moontown: A history of Chanthaburi, [www.ruby-sapphire.com]

Richard W. Hughes and Vincent Pardieu, with Michael Rogers, Olivier Segur and Philippe Ressigeac (2010- last update): Red Sky at Dusk: Hunting the Last Siamese Ruby Miner, [www.ruby-sapphire.com]

Pongsak Vichit (1975): Origin of corundum in basalts, Master thesis, New Mexico Institute of mining and technology.




Corundum
Al2O3

Corundum Size 55 x 39 x 29 mm © Oleg Lopatkin


Corundum has been known from Vietnam since it was a French colony, but these early finds had no commercial value. It was not until gem quality ruby was found near An Phu and Ham Yen in the Yen Bai Province in 1983 more through investigations were initiated. Vietnam’s government got interested, and in 1987, large ruby deposits were discovered near Luc Yen. In 1988, the Vietnamese government established the company Vinagemco to manage the gem mining. The government’s attempts to control the mining has not been very successful, as a large number, in periods thousands, of illegal miners have swarmed the mining areas in search for gems. In the 1990-ties a there was a veritable ruby Klondike in Vietnam, drawing in particular Thai gem traders to the country. After 2000 the activity seems to have dropped somewhat, possibly due to a more stable production, or because new finds in Madagascar around that time sparked more interest with the traders.
Corundum has nevertheless been found in a variety of geological environments in both hard rock and in placer deposits. It is undoubtedly the rubies of the Luc Yen district that are most known and most sought after, but some of the other localities may also produce interesting specimens.
As a mineral collector I would like to see more corundum specimens out of Vietnam, but it does not seem that the mineral collector marked can prevent the best specimens from ending up as jewelry.

The following text gives a brief overview of the Vietnamese corundum localities,

Corundum
Vietnam
Bac Kan Province, Ba Be district

Colourless to pale blue sapphire is found in a pegmatite, composed of quartz, K-feldspar and muscovite, which intrudes schist and marble. The corundum here is relatively small, and not of outstanding quality. The occurrences of corundum in a granite pegmatite is however quite interesting and rare.


Corundum
Vietnam
Binh Thuan province, Da Ban area

The localities in Dak Nong, Da Ban and Ma Lam are all in the southern part of Vietnam. The corundum here is found in placers formed from eroded alkali-basalt flows.. The corundum is normally 2-7mm long barrel shaped crystals, but crystals up to 30-40mm are known. The colour is normally dark blue. The alluvial corundum sometimes shows glassy-looking margins that indicate high temperature corrosion—indirect evidence of magma transport. In the Da Ban area megacrysts of dark-blue sapphires are sometimes found within alkali-basalts thus proving their origin.


Corundum
Vietnam
Dak Lak province, Dak Nong area

Here the sapphires are found in weathered residual soils lying above the flows and also in the river and stream fans. Generally, the alluvial corundum corresponds to xenocrysts found in situ in basalts . The colour of the sapphires ranges from dark blue, through blue, green to yellow. The crystals occur as broken fragments, but with prismatic and bipyramidal shapes and dimensions of up to 1.5 cm long and 0.2-0.4 cm wide


Corundum
Vietnam
Nghe An Provin ce, Quỳ Châu district

The Quy Chau deposits lie within the Bu Khang ruby zone of central Vietnam. Corundum is reported to occur in a 2,000 km2 large area near Bu Khang Mountain, with a 400 km2 zone that appears to have the best ruby bearing potential. I have considered these localities as a unit since the corundum found at these localities are similar and formed by the same geological processes., even though there are several mines and diggings in the area.
The Bu Khang dome cosists of Paleozoic and Mesozoic sedimentary and metasedimnetary rocks overlying a core of mica schists, granitoids and gneisses. Ruby and blue sapphire (rare) are found in and near Quy Chau, where a major Cenozoic shear zone form the Northeastern boundary of the Bu Khang dome.
Although some corundum are found in hard rock, it is mostly found and extracted from placer deposits. The gem material consists of ruby, with smaller amount of blue to violet and orange sapphire. Ruby tends to be slightly purplish red in hue position; their crystals are usually in hexagonal prism and barrel shape. The rubies have been found associated with tin minerals in Quaternary sediments. Analysis of O-isotopes and fluid inclusions indicates that the corundum is of a metamorphic origin, but the origin of these gems remain unclear.

Rubies and sapphires have been mined since 1987 from the placer deposits of Doi Ty, Doi San, Mo Coi and Quy Hop. The gem bearing gravel normally forms a 1-8m thick layer buried under 3-7m of clay and soil.

Corundum
Vietnam
Quang Nam Province, Phuoc Hiep occurrence

Corundum is found in placers eroded from high‐grade metamorphic rocks (typically of amphibolite‐granulite facies), of volcanosedimentary origin, such as garnet‐bearing amphibolites, gneisses and schists, intruded by igneous formations of different composition and age.

To date, the rubies and fancy sapphires have been found in secondary, mostly alluvial deposits. The corundum crystals occur as broken, from moderate‐ to well‐rounded, fragments, but remains of the original habits are often present. Their size ranges from 3×5 mm to 20×30 mm, sometimes to 100×120 mm. Most of corundum pieces are of purplish pink to purplish red, with a small proportion of light to dark blue.


Corundum
Vietnam
Yenbai (Yen Bai) Province, Luc Yen

The Luc Yen district is the Vietnamese centre for ruby and sapphire trade, and each morning gem trades gathers in the Yên Thé (often reffered to as Luc Yen city) market selling raw gems, mineral specimens, heat treated gems, gem paintings made of finely crushed gems of different colors as well as marble figurines delicately using the red and green of small embedded ruby and pargasite crystals in the design. In theory, the Luc Yen gem market should be possible to visit on a day trip from Hanoi, in reality the 100km trip takes longer, and one or more overnight stays are recommended by those who have been there.

There are several mines and workings in the Luc Yen district and it may be difficult to find the exact origin for a specimen acquired in the Luc Yen or Hanoi gem markets and the corundum found there are very similar in terms of origin and appearance. The corundum from Luc Yen is predominantly pink to red and purple, and blue and colourless sapphires coexist with rubies as well as with grey to brown and bi-pyramidal sapphires and trapiche rubies. Most of the gem-quality material ranges from 2 to 6 mm long, but gem rough up to and exceeding(?) 20 carats can be found. Larger non-gemmy crystals around 2 cm are not uncommon, and larger crystals up 5 cm are known. Display size specimens with multiple, well formed ruby crystals in white marble are known.

Since it’s discovery, the Luc Yen localities has been the subject for extensive research. Geologists, mineralogists and gemologists have investigated trace elements, inclusions, mineral association and geological history of the corundum bearing rocks. Many publications are available online, as can be seen from the reference list here.

The gem corundum contains Chromium (0.19 to 2.08 wt.% Cr203), )as the most abundant trace element, followed by smaller amounts of titanium (0.01 to 0.23 wt.%TiO), iron (0.01 to 0.30 wt.% FeO), and vanadium (0 to 0.03 wt.% V203]. Small amounts of Zn and Ga were also found . Higher (Fe+Ti)/Cr ratios give purplish stones.

Analysis of inclusions in the Luc Yen corundums has revealed 28 differne minerals, among them rarities such as monazite.

Corundum can be found either in solid rock, or in alluvial placers. The primary deposits are linked with the formation of the Red River shear zone. The Red River fault system constitutes the Day Nui Con Voi metamorphic belt (DNCV) formed by high grade sillimanite–biotite garnet gneiss and micaschists. These gneisses contain various leucosome and leucocratic magmatic dikes. Marbles and amphibolites are locally interlayered within the garnet micaschists. The ruby deposits occur in the Lo Gam zone in a thick metasedimentary sequence of Cambrian age, composed of marble and overlying sillimanite – biotite – garnet schis. These units, bounded by left-lateral faults, are intruded by granitic rocks and related pegmatites of Triassic age. Gem corundum occurs in three distinctive environments:

• disseminated crystals within marbles with phlogopite, dravite, margarite, pyrite, rutile, spinel, edenite and graphite (Bai Da Lan, An Phu, Minh Tien, Nuoc Ngap, Luc Yen and Khoan Thong mines);
• veinlets associated with calcite, dravite, pyrite, margarite and phlogopite (An Phu mine);
• fissures with graphite, pyrite, phlogopite and margarite (Bai Da Lan mine); Minh Tien region (Fig. 5).

The alluvial corundum are found together with gem spinel and some gem garnets and tourmalines. The placer deposits are found in 130 x 2-5km belt of metasedimentary marbles and crystalline schists and quartzites in narrow karst like depressions and valleys and are extracted by removing the top soil before washing the gem bearing gravels. Often several meters of soil and clay cover the gem bearing gravels.

Corundum 3.4 x 3.3 x 2.3 cm specimen © Rob Lavinsky
,
Corundum 5 x 4,2 cm specimen © JSS
Corundum 16 mm crystal © 2001 John H. Betts

Corundum 2.1 cm © Rob Lavinsky
Corundum 5.7 cm © Rob Lavinsky
Corundum 2,1 cm © Rob Lavinsky



Corundum
Vietnam
Yenbai (Yen Bai) Province, Luc Yen, An Phu

Corundum 7,6 cm tall © Dan & Diana Weinrich Minerals

The An Phu mine near An Phu village in the Luc Yen mining district, Vietnam has been the source of attractive specimens of ruby corundum and large purple to red spinel crystals, as well as phlogopite, pyrite, dravite and green edenite crystals embedded in white marble matrix. However, the pegmatitic tourmaline and beryl that have also been labeled as coming from An Phu are actually from the nearby Minh Tien pegmatite. This mine is a primary ruby deposit and is the source of most of the ruby-in-matrix carvings available in Vietnam.
The An Phu mine was one of the initial ruby producing localities in Vietnam.


Corundum
Vietnam
Yenbai (Yen Bai) Province, Yen Bai

Corundum is also found at multiple locations near the Yen Bai city, further south than the Luc Yen area. It appears that the Yen Bai localities often are considered part of the Luc Yen ruby field. From a political boundary point of view, this is not fully correct, but the geology of the two neighboring provinces are very similar, and from a geological perspective it’s the same thing.

Also at Yen Bai, the corundum are found in the Day Nui Con Voi metamorphic belt (DNCV) in the Red River Shear Zone. The Day Nui Con Voi range is composed of high grade metamorphic rocks with sillimanite-biotite-garnet gneisses, mica schists with local successions of marble and amphibolites. The rocs are metamorphosed to amphibolite facies (4-6,5kbar/600-750 deg C), and corundum occurs as

A) as grey to blue sapphires in garnet-sillimanite-mica schists and gneisses containing granitoid dykes
B) )as cm sized gray to dark grey corundum in biotite schists formed by metasomatic action on amphibolite
C) as rubies in metasedimentary marble layers intergrown with gneiss, micaschist and amphibolite

The area is also notable for ruby crystals that form within an outer crust of spinel, which is also frequently found at a number of the mines in the area.

There are several mines and workings around Yen Bai, and I will only address the most important in this text.


Corundum
Vietnam
Yenbai (Yen Bai) Province, Yen Bai, Tan Huong mine

Various qualities are found at several of the localities, but it is worth singling out Tang Huong for the production of star rubies with very nice sharp natural asterism that looks almost as good as that found in diffused stones. Ruby was firdst found and exploited by local farmers in 1994. In 1996, the deposit was managed and exploited by the Vietnam National Gem and Gold Corporation (VIGECO). From 1994 to 1996, hundreds kilograms of rubies and star rubies were exploited illegally. The VIGECO operation is now shut down, but private miners still produce rubies in the vicinity of the now closed main mine.

Ruby and spinel have been found in the magmatic rocks in minor grains as well as in marbles (Nguyen Kinh Quoc et al. 1995). In placers, ruby grains are eroded but the crystals present a prismatic shape, are from 1.0 to 19 mm long, and range in colour from red to reddish and purplish to red. The main associated gem mineral are red and octahedral spinels and blue trapiche-like sapphires. In April 1997, two ruby crystals of 2.58 kg (The star of Vietnam) and 1.96 kg (star ruby) respectively, of very high quality, were found and declared State treasure.


Corundum
Vietnam
Yenbai (Yen Bai) Province, Yen Bai, Truc Lau

At the Truc Lau occurance, rubies and blue sapphire are found in a 5 m thick gravel layer overlain by a 3.5 m of quaternary sediments and 1-1.5 m of soil. In 2002, up to two boulders (1-2 kg) per month made of pink sapphire and star ruby were recovered from this paleoplacer. (Pham Van Long et. Al 2004)


Literature:

Dudley Blauwet(2006): The sapphire and spinel deposit of An Phu: Luc Yen mining district, Yenbai province, Vietnam.The Mineralogical Record

M. P. SEARLE (2006): Role of the Red River Shear zone, Yunnan and Vietnam, in the continental extrusion of SE Asia, Journal of the Geological Society, London, Vol. 163, 2006, pp. 1025–1036

Anna ŚWIECZEWSKA, Anna WYSOCKA, Sławomir ILNICKI, Nguyen Quoc CUONG and Dong Pha PHAN (2006) , Record of Motion Along the Red River Fault Zone in Provenence Studies, Northern Vietnam, GeoLines 20

Robert F. Kane, Shane F. McClure, Robert C. Kammerling, Nguyen Dang Khoa,Carlo Mora, Saverio Repetto, Nguyen Duc Khai, and John I. Koivula(1991): Ruby and fancy sapphire from Vietnam, Gems and Gemmology

Nguyen Ngoc Khoi, Nguy Tuyet Nhung, Nguyen Thi Minh Thuyet*, Phan Van Quynh(2007): Characteristics of corundums from Phuoc Hiep occurrence (Quang Nam Province), VNU Journal of Science, Earth Sciences 23 (2007) 152‐158

Pham Van Long, Hoang Quang Vinh, Virginie Garnier, Gaston Giuliani, Daniel Ohnenstetter, Therese Lhomme, Dietmar Schwarz, Anthony Fallick, Jean Dubessy and Phan Trong Trinh(2004): Gem Corundum deposits in Vietnam, Journal of Gemmology, 2004, Vol 29, number 3, pp129-147

Chakkaphan Sutthirat, Sarawut Lapngamchana, Visut Pisutha-Arnond and Nguyen Ngoc Khoi (2008): Petrography and Some Mineral Chemistry of Gem-Bearing Marble from Luc Yen Gem Deposit, Northern Vietnam, Proceedings of the International Symposia on Geoscience Resources and Environments of Asian Terranes (GREAT 2008), 4th IGCP 516,and 5th APSEG; November 24-26, 2008, Bangkok, Thailand

Gaston Giuliani, Jean Dubessy, David Banks, Hoang Quang Vinh, Therese Lhomme, Jacques Pironon, Virginie Garnier, Phan Trong Trinh,Pham Van Long, Daniel Ohnenstetter, Dietmar Schwarz(2003): CO2–H2S–COS–S8–AlO(OH)-bearing fluid inclusions in ruby from marble-hosted deposits in Luc Yen area, North Vietnam
Chemical Geology 194 (2003) 167– 185

VIRGINIE GARNIER, DANIEL OHNENSTETTER, GASTON GIULIANI, HENRI MALUSKI, ETIENNE DELOULE, TRINH PHAN TRONG, LONG PHAM VAN, VINH HOÀNG QUANG(2005): AGE AND SIGNIFICANCE OF RUBY-BEARING MARBLE FROM THE RED RIVER SHEAR ZONE, NORTHERN VIETNAM, The Canadian Mineralogist Vol. 43, pp. 1315-1329 (2005)

Christoph A. Hauzenberger, Tobias Häger, Wolfgang Hofmeister, V.X. Quang, G.W.A.Rohan (2003): Origin and formation of gem quality corundum from Vietnam, "Geo- and Material-Science on Gem-Minerals of Vietnam"
Proceedings of the International Workshop, Hanoi, October 1 - 8, 2003

Vincent Pardieu and Jean Baptiste Senoble(2005), An update on Ruby and Sapphire mining in South East Asia and East Africa.Vietnam 2005, www.fieldgemmology.org

Vicent Pardieu, Kham Vannaxay, Sofragem(2010): "Gems and pearls from Vietnam - An update", GIA Networking Evening in 2010

Pham Van Long, Gaston Giuliani, Virginie Garnier, Daniel Ohnenstetter(2004): Gemstones in Vietnam, A review, The Australian Gemmologist, Volume 22, Number 4, October–December 2004


Olav Revheim 2012

Click here to view Best Minerals C , and here for Best Minerals A to Z and here for Fast Navigation for finished Best Minerals articles.



Edited 19 time(s). Last edit at 03/24/2014 12:08PM by Olav Revheim.
Re: Corundum Vietnam
January 23, 2012 09:23PM
    
Rock,

Is it possible to create a "Best Minerals-Corundum" tab one level up in the hierarchy the same way as it has been been done for "Best Minerals- Calcite" and "Best Minerals Quartz". I have made two country articles so far, Corundum USA and Corundum Vietnam.

There will be more of them, probably

Corundum Canada
Corundum Europe
Corundum India
Corundum Madagascar
Corundum Tanzania
Corundum Africa
Corundum Asia
Corundum Australia

and possibly a few more.

Olav
avatar Re: Corundum Vietnam
January 23, 2012 11:47PM
Yes, it is possible, however if we start doing that for every mineral it is going to make the whole thing pretty huge. The only reason that I went to multiple countries in things like quartz is that I ran out of space in these fields, which only hold about 60,000 characters. I just kept adding to the fields till I got a message that I had run out of space and at that point I made a decision how to split the things up. I would suggest you just keep adding to corrundum till you run out of space. I have a feeling that you probably won't run out of space on Corundum. Corundum has a lot of localities, but not compared to quartz, or calcite or pseudomorphs.

Rock Currier
Crystals not pistols.
Re: Corundum Vietnam
January 24, 2012 07:05AM
    
Rock,

I did run out of space, that's why I had to create the Corundum USA article. I agree that the number of these "multiple entry" minerals should be kept a minimum, so if you want to keep corundum as-is that's fine with me, but there will be more entries.

I can try to keep the number of entries as few as possible, maybe one entry pr. continent or something similar.

smiling smiley

Olav
avatar Re: Corundum Vietnam
January 24, 2012 03:56PM
    
Probably the best way to handle them now is the way Rock handled azurite.
[www.mindat.org]
Re: Corundum Vietnam
January 24, 2012 08:22PM
    
That's a good idea David. Either like Rock did for Azurite or by continent I think. smiling smiley

Olav
avatar Re: Corundum Vietnam
January 25, 2012 03:40PM
Sounds good!

Rock Currier
Crystals not pistols.
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