2007: Chantaburi has changed a lot since 1973. There are new types of colored stones coming from Africa, South Asia, and Southeast Asia + good quality rubies and sapphires are getting more difficult to find + foreign tourists, dealers, students are still visiting Chantaburi looking for the best deal and making mistakes.
(via The Journal of Gemmology, Vol.13, No.8, October 1973) J A L Pavitt writes:
Thailand, or Siam as it was formerly named, is a well-known source of sapphire, ruby, star-sapphire and zircon and over the years the skill of Thai lapidaries has advanced to a very high degree, making Bangkok, the capital city, an important center for the supply of cut gemstones.
There are a number of gem mining localities in Thailand, many of them in remote areas, but the mines at Chantaburi (also known as Chantabun), 200 miles from Bangkok, can be reached by car in five and a half hours, and soon after our arrival in Thailand in 1971 my wife and I made our first visit to Khau Ploi Waen, or ‘Hill of the Sapphire Ring’, as this mining area at Chantaburi is named. I have since made further visits, the most recent in January 1973 with Mr Kenneth Parkinson during his two week visit to Thailand.
Chantaburi has a very special place in the history and culture of the Kingdom of Thailand. Situated near the coast, only thirty miles from the border with Cambodia, its inhabitants, although loyal and proud Thai nationals have ethnic origins connecting many of them with the diverse civilizations which existed thousands of years ago between the borders of China and the Mekong Delta. These origins are still evident in the customs, skills, religious and dialects to be found among the people of this fertile eastern region of the Kingdom.
It was at Chantaburi that King Taksin marshaled his forces after the fall of the ancient city of Ayuthaya, and finally defeated and drove out the Burmese invaders. Close to the sapphire mines one can see the rusting cannon and remains of the fortress of King Rama III (1787 – 1851).
The gem-bearing deposits at Khau Ploi Waen are about six miles south of the town of Chantaburi, near the village of Ban Kacha. Past records indicate that in 1850 the Shans and Burmese were extracting sapphires here and that in 1850 a British Company obtained a lease but failed to make a success of the venture. In 1919 the Siam Mining Act came into force and since then mining has been solely in the hands of Thai nationals.
The mining area is privately owned and has been cleared of primary growth and planted with rubber trees, although it is obvious that an income from rubber tapping is of minor importance. A lease to dig for gemstones over an area of one ‘rai’ (approx. 0.4 acre) for one year is granted by the landlords for a fee which may be as high as baht 300000 for high yield areas which have not previously been worked. A lease is usually shared by groups or families and there are said to be some 2000 people mining around Khau Ploi Waen.
The method of extracting the stones is very primitive, as are the tools—a pick, a spade and a rattan basket. A vertical shaft of about four feet in diameter is dug in the red/brown clay soil, in between the rubber trees. These vertical shafts sometimes go as far as thirty feet deep and each basketful of soil is lifted to the surface by a crude, but effective, crane arrangement consisting of two bamboo legs and a long bamboo derrick arm with a rope and basket at one end and a counterbalance of large stones tied to the other end.
When a gem-bearing stratum is reached each basketful of soil is placed to one side at the top of the shaft, to be washed and sorted. In some instances a horizontal shaft will be dug to follow the gem-bearing stratum, but as no wooden props or tunnel shores are used the length of these horizontal tunnels is limited by the courage and tenacity of the digger, not to mention his ability to breathe in the tomblike atmosphere. No ladders are provided in the vertical shaft, and entry and exit are effected by bracing the back and hands against one wall and the feet against the opposite side, at the same time exerting the body in a motion that would do credit to James Bond in tightest spot.
There is no natural supply of water for washing the extractions, so the miners pay for this to be brought from the nearby village by water-tank lorries. A small pond about ten feet in diameter and three feet deep is formed near the shaft and the baskets of soil are washed and broken up by members of the group sitting in the pond. As and when the gemstones are found, these are placed in small plastic bags around the perimeter of the pond.
This particular area produces a fair quantity of corundum, most of the crystals being in the form of repeated lamellar twinning. In this form some of the stones can be cut en cabochon to exhibit fine golden six-rayed stars on a dark brown to nearly black background, and on my visit I met Khun Saengroong, a local dealer and cutter, who had just bought a magnificent hexagonal lamellar crystal of star sapphire material weighing 1720 carats. This is of course a rare exception and the average size seldom exceeds 15 carats, and even then only very few of the stones will, when cut, show a well-centered star without the disfiguration of the prominent zone lines which are a feature of the stones from this mine.
The local ‘test’ for rough star sapphire material is to place a drop of water on the stone and to view it from an overhead single light source. In a suitable crystal the ‘star’ will show up clearly when the drop of water is placed in the right position. As it is to be expected, a very great proportion of these opaque corundum crystals show a very poor, or no, star-effect, and these fetch very low prices.
In quantity, the second main gem production of this area is green sapphire, followed by blue/green, yellow/green and more rarely fine blue and yellow sapphire. The hexagonal zoning is easily detected under the lens in a large majority of these stones.
Also associated with the corundum are pyrope garnet (R.I=1.745-1.750) and a fairly large quantity of opaque black stones which take a high polish and are sold both faceted and en cabochon as ‘Thai Jet’. Kenneth Parkinson took ten of these back to the U.K and has since written to tell me that seven of these have a S.G of between 4.1 and 4.2 and with a R.I just visible at the very end of the standard refractometer it seems fairly certain that they are black almandines. The other three stones proved to be black diopside (no star or cat’s eye) with a clear double refraction 1.68 – 1.71. Although this is slightly higher than the normal 1.67 – 1.70, Webster (Gems, 2nd Edition, page 264) notes that the R.I may rise when the material is so dark as to be virtually hedenbergite.
Many jewelers and gem dealers in Bangkok will inform their customers ‘These stones come from our own mine at Chantaburi’, but it is very doubtful whether any of them actually engage in mining themselves, as those who have taken a lease and employed people to dig for them have usually found that somehow their area seems to produce only low-grade stones. The best quality stones will find their way into the market, but not through the lease-holder. The local expression is ‘employ someone to dig and your stone will fly.’
Dealers and middlemen gather at a small group of wooden coffee shops at the fork of two roads leading into the mining area and it is here, in the late afternoon, that the miners bring their daily production for sale.
The existence of these sapphire mines and others in the area producing ruby and zircon, has created a flourishing cutting and setting center in the town of Chantaburi. The standard of work is high, and compared with western prices, cutting costs are very low. A skilled Thai lapidary will be paid about 20 pence for faceting and polishing a zircon of one carat. These low cutting costs have prompted many of the local dealers to import rough gem material for cutting in Thailand and eventual export to the major markets in Europe and the USA. When Kenneth Parkinson and I were in Chantaburi we were shown a parcel of fine blue sapphire crystals recently purchased in Australia. One could not help thinking of the expression ‘bringing coals to Newcastle’.
Although sapphire, ruby and zircon are the principal materials cut at Chantaburi, opal, emerald and other rough is imported for cutting. It is perhaps inevitable that half boules of synthetic corundum are to be seen in many of the gem cutting shops, and, although the majority of dealers will not offer synthetics as anything but what they are, one suspects that a few will be sorely tempted when selling to some of the gullible foreign tourists who are now starting to visit this area.
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