A peculiar feature connected with "byon" is its occurrence in caves in the limestones. These can be traced for miles underground, now as wide and high chambers or vaults, now as small crevices and narrow cracks. These caves are either wholly or in part filled with the "byon", which is usually covered over with a thick deposit of calcareous tufa in stalactites and stalagmites of the most fantastic shapes.
Previous to 1886, exclusively the natives, who adopted methods differing according to the conditions, mined the deposits. In alluvial deposits in the valleys the "byon" layer was reached by excavating pits ("twinlones"), 2 to 9 feet square. When the excavation was made in loose, crumbling material the sides of the pit ware supported by bamboo. From the bottom of the pits ware driven horizontal galleries from one pit to another, so that as much as possible of the gem-bearing earth may be excavated. The light, earthy part of this material was removed by washing, and the remaining sand then searched for precious stones. The actual work of excavating could only be undertaken in the dry season of the year.
The ruby-bearing layer on the sides of the hills was reached by means of open cuttings or trenches ("hmyaudwins"). Their excavation was usually effected by means of running water, which was led in bamboo pipes often over considerable distances to the spot where it was required. The flow of water thus obtained washed away the superimposed debris and all the lighter part of the gem-bearing layer, leaving the heavy precious stones behind. This kind of work was naturally carried on in the rainy season, since large volumes of water ware required.
Finally, we come to the "loodwins", or workings in the gem-bearing material, filling the limestone caves. This material was excavated and washed for precious stones in the ordinary way. The workers in cuttings on the hillside occasionally came upon limestone caves; especially large ones were found, from time to time, in the Pingudaung Mountain near Kyatpyen.
The mines situated in the alluvial deposits of the river valleys are the most important, and the greater part of the yield was derived from the mines in the valleys in which stand the towns of Kyatpyen, Kathay, and Mogok, the latter valley being especially rich. The cave deposits ware probably rich enough to pay for the introduction of European mining methods; the primitive efforts of the natives ware attended by great danger and loss of life, and by very meager returns.
In former times intending miners were obliged to procure a license before undertaking any work; they were also required to pay a tax and to hand over to the king all stones exceeding 1,000 rupees in value. Whether the finder of such a stone received anything in return for it depended entirely upon the caprice of his sovereign. It was natural that attempts should be made to evade this obligation; many large and valuable stones were broken up into pieces small enough to be legitimately retained by the finder, while others found their way into the hands of illicit dealers.
Persons desirous of trading in rubies were required to obtain the permission of the Government of Burma, and were subject to a special tax. The monthly yield of stones was about 50,000 to 100,000 rupees worth, and before being put on the market they had to be taken to the Ruby Hall in Mandalay. Side by side with the legitimate trade there flourished a trade in smuggled stones, the finest of which found their way through Lower Burma into India, being in many cases sold in Calcutta. In the time of the last king of Upper Burma (deposed in 1886) it is said that the illegitimate trade in rubies in Lower Burma amounted to between two and three times the official trade per annum.
Thousands of small rubies with rounded surfaces, rudely fashioned, are set in a great variety of articles belonging to the Burmese regalia. These were taken from the palace of King Theebaw at Mandalay at the time of the British conquest of Upper Burma, and are preserved in the Indian section of the Victoria and Albert Museum at South Kensington.
In 1886, when Burma became part of the British Empire, the monopoly of the ruby mines by the natives came to an end. In the neighborhood of Mogok work on a large scale was carried on first by an Anglo-Italian and then by an English company. In return for the concession of mining rights the Indian Government demanded from the company a yearly payment of four lacs of rupees (about $2,716,400), and from each native miner at first twenty, and afterwards thirty, rupees. The operations of the company have not been altogether successful. Not content with working the alluvial deposits of the valleys in which rubies have been searched for centuries, the company has also tapped the ruby bearing deposits on the Pingudaung Mountain, near Mogok, and on the Kyuktung Mountain.
The"byon" yields not only ruby but also other color-varieties of precious corundum, namely, sapphire, "oriental topaz" etc., common corundum, and frequently precious spine. Besides being the most valuable and beautiful of the different varieties of corundum the ruby is here also the most abundant, about 500 rubies being found to one sapphire, and other color-varieties of precious corundum are still more rare. The unequal proportions in which ruby and sapphire exist in these deposits are partly counterbalanced by the much greater size of the crystals of sapphire. The majority of the rubies found here do not exceed 1/8 carat in weight, and large stones, when found, are often full of all kinds of faults. Flawless stones of 6 to 9 carats are rare, and very few reaching a weight of 30 carats have ever been found.
In the year 1887 a stone of 49 carats was found, and in 1890 one of 304 carats. The discovery in earlier times of two stones of 172 and 400 carats has been reported. The King of Burma sold the two most beautiful rubies found here in Europe in 1875. Both were of a magnificent color, and before they were recut weighed 37 and 47 carats. After being recut in Europe they sold for £10,000 ($1,086,550) and £20,000 ($2,173,100) respectively. Cloudy corundum unsuitable for cutting as gems because of its lack of transparency occurs in much larger pieces, some of which have weighed over 1,000 carats. Streeter offered a stone of this description weighing 1,184 carats. This, together with other stones of exceptional size, was found since the English occupied the country. On the whole, the proportion of large rubies found in the mines of Burma seems to have increased, but in almost every case these large stones are unfit for cutting as gems.
The color of the rubies of Upper Burma is, as a rule, some shade of deep red. In that country the shade most admired is pigeon's-blood red. Stones of this color, transparent and free from faults, command high prices even at the mines. Rubies of a poorer tone of color are also found, but not as frequently as in Ceylon, where they predominate over the stones of deeper shades.
When found embedded in its original matrix, namely, the white crystalline marble, the ruby has always a regular and well-developed crystalline form, diagrams of which are shown in Fig. a to d. When found in the gem-earths this symmetrical form is not always missing, though, as a rule, rubies from this deposit are irregular in outline, while those picked out of the alluvial sands of the river valleys are usually much rounded. It is the custom among the natives not to sell a ruby in its natural form, but to give it some artificial shape or another, usually quite irregular and not calculated to enhance the natural beauties of the stone. Such specimens have to be recut in Europe. The two large rubies, for example, which came to Europe in 1875, were roughly cut en cabochon. By recutting the weight of the one was reduced from 37 to 32 5/16 carats and of the other from 47 to 38 9/16 carats. The native lapidaries are for the most part settled at Amarapura near Mandalay.
Almost all the Burmese rubies ware found in the district around Mogok. Valuable stones, however, are reported to have been found in the river gravels of the Nampai valley near the village of Namseka, which lies fifteen miles south-west of Mainglon, in latitude 22° 46' N. and longitude 96° 44' E. Assuming this occurrence to be a fact, Dr. F. Noetling explains it by supposing that the gravels in this outlying district have been washed down from the ruby-bearing area by the Mogok stream when in flood. At the time of Dr. Noetling's visit a large excavation had been made in these gravels; in them he found spinel, tourmaline, etc., but his search for rubies was unsuccessful.
A second ruby district in Upper Burma, less important, however, than Mogok, exists in the neighborhood of Sagyin, twenty-one miles north of Mandalay. Here a range of low hills built of crystalline limestone rises up out of the alluvial plain of the Irrawaddy, itself two miles distant. This white marble is for the most part overlain by red clay; it is much creviced and penetrated by caves, and indeed in all respects closely resembles the marble of Mogok. The ruby has here two modes of occurrence. In places in which the marble contains few or no embedded rubies, its crevices are often filled up by fragments of the same rock, rich in rubies and firmly cemented together. In other cases the crevices and caves in the limestone are filled, just as at Mogok, with brown clayey material produced by the weathering of the limestone. In this are found the precious stones together with other minerals, namely, ruby, sapphire, red and black spinel, amethyst, brown chondrodite, very pale blue apatite in small grains and crystals, reddish-brown mica, etc. The precious stones are separated from this weathered material by washing. A more systematic working of the deposits would be likely to yield better results. The rubies found here are sometimes said to be paler and inferior in quality to those from the Mogok district, but many observers dispute this statement.
It is asserted that rubies have been found, associated with spinel and as usual embedded in granular limestone, at a place further north, near the village of Nanyetseik, between Mogaung and the jadeite mines of Sanka; also at still another locality on the Upper Irrawaddy. According to native reports, rubies and spinels occur in the limestone of two hills lying a little to the north of the Sagyin Hills. It may be mentioned finally that during the construction of the railway from Rangoon to Mandalay, abandoned ruby mines were met with near the town of Kyoukse, about thirty miles south of Mandalay.
The occurrence of rubies in Siam has been long known and the deposits have been carefully investigated and systematically worked. Prospecting for precious stones in this country was for long rendered impossible or, at least, extremely difficult by the exercise of royal and official privileges. Later, however, an English company, known as "The Sapphires and Rubies of Siam, Limited", has obtained a concession of mining rights in this country. Mr. E. W. Streeter gives details of the workings in his book, "Precious Stones and Gems".
Though some of the Siamese rubies equal those of Burma in beauty, the majority ware very dark in color and generally inferior. The mines ware situated in the provinces of Chantabun and Krat; a few rubies ware found also in the sapphire mines of Battambang, southeast of Bangkok.
The mines of Chantabun ware about twenty hours journey by steamer from Bangkok. They were not far from the coast of the Gulf of Siam, and near Chantabun, the capital of the province of the same name. The lofty mountains of this region consist of grayish granite, and the lowlands of limestone. The latter may possibly be, as in Burma, the mother-rock of the ruby. At present the precious stone is only known to occur in sands, which have hitherto been worked for long by the most primitive methods by the natives. The workers ware for the most part Burmese, and their usual method of working the deposits was to excavate a small shaft, which never exceeded 24 feet in depth. Precious stones were at one time very abundant in this region; according to a missionary report of the year 1859, it was possible in half an hour to collect a handful of rubies from the "Hill of Gems", an eminent hill standing to the east of the town of Chantabun. This particular accumulation is now dispersed, but the town of Chantabun remains the center of the trade in precious stones of this region.
Rafal Swiecki, geological engineer email contact
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