June 08
Thomas Henry Digges La Touche (1856–1938)
By THAN HTUN
(GEOSCIENCE MYANMAR)
EPISODE:13
Thomas Henry Digges La Touche (1855-1938) following schooling in Shrewsbury was awarded a degree in Geology in 1880 under Professor Hughes at St. Johns College Cambridge. He joined the Geological Survey of India in October 1881, two years after R. D. Oldham (1858-1936), and was, when he retired, one of the few geologists to complete 25 years in the Geological Survey of India.
La Touche married Anna (Nancy) Handy in 1891. Although Nancy accompanied him on his early fieldwork, the arrival of children and his appointment to remote field areas led to long separations, often exceeding 8 months and on one occasion last two years. Each year fieldwork started in October and continued to March, and the findings of the work were written up in the recess during the hot summer months in headquarters in Calcutta. Throughout the time of these prolonged separations, Tom and Nancy wrote to each other daily. Tom’s letters to Nancy and the children, who lived initially in the hill stations of India, and eventually in Ireland, thus form a fairly continuous diary of important events and affairs in the office, and in the field. More importantly, they provide an illuminating view of the lifestyle and personal interactions of the dozen Geological Survey Officers who were based in Calcutta. La Touche was appointed Acting Director when Sir Thomas Holland went on leave on 2 August 1909 until his retirement in 1910. He died in 1938 at Cambridge aged 82, two years after Oldham, having just read the proofs of his final work, a massive compilation of geological locations in India with their geographical coordinates.
La Touche reported the economic minerals of Burma in his “Indian Minerals of Economic Value” in 1918. Of all resources the ruby and jadestone could be extracted as follows: –
Ruby
The ruby mines of Upper Burma have long been known as the principal source of the world’s supply of the gem. Caesar Fredericke, who visited Pegu in 1569, alludes to the brisk trade in rubies that was then carried on; and reference to the mines was also made about the same time (1586) by the English traveller Ralph Fitch who places them in the district ‘Caplan’ (Kyatpyin), five days journey from Ava. Neither of these travellers was permitted to visit the mines, and the first authentic account of them was given in 1833 by Pere Guiseppe dÁmato. He describes the workings at KYATPYIN (22˚ 53’30”: 96˚28’), and the system of mining practised by the Burmese, which may still be seen in operation in that neighbourhood.
Three distinct ruby tracts are known to occur in Upper Burma, widely separated from each other; but in all cases, the original source of the gems is found to be a highly crystalline limestone, probably a member of the Archean group. A fourth tract is reported to have been discovered in the Moemeik State in 1913, but as yet no definite information regarding this occurrence has been published.
Mandalay: Sagyin (22˚ 17’ : 96˚ 7’). About the year 1870, these mines were in charge of a Mr Bredemeyer, whose account of them is referred to by Ball. The locality was reported on by Hayden in 1895. A group of hills, composed of crystalline limestone largely quarried for statuary marble, rises abruptly from the alluvial plain on the left bank of the Irrawaddy, about 16 miles to the N. of Mandalay. Moisture, acting along the joint planes of the rock, has caused it to become scammed with fissures and hollows, filled with the insoluble clayey material supplied by the disintegration of the limestone. These fissures are followed up and the material extracted from them is washed. Sapphires and spinels, as well as rubies, are obtained here.
Myitkyina: Naniazeik (25˚ 37’ : 96˚ 37). The ruby tract of Naniazeik was first brought to notice in 1895, when it was examined by Warth, who reported that rabies, sapphires, and spinels are obtained from the detritus afforded by the disintegration of crystalline limestones surrounded by intrusive masses of granite. A full description of the tract has since been given by Bleeck, and the petrology of the area has been studied by Tanatar. Neither ruby nor spinel appears to be very abundant in this tract and no output has been reported for the last twelve years. Bleeck also mentions a small ruby tract, worked with poor results by the Kachins, on a hill stream 4 miles to the N. of Manwe (25˚ 26’: 96˚ 35’), and some deserted ruby pits said to lie 13 miles to the N. W. of Naniazeik.
Mogok: Ruby Mines (22˚ 55’ : 96˚ 33’). In this district, the crystalline ruby limestones form a series of narrow, parallel, lenticular bands, distributed in echelon along the southern flanks of a range of hills extending from the neighbourhood of Mogok, where the most productive mines are situated, to Thabeikkyin on the Irrawaddy, a distance of about 40 miles in a direct line from east to west. The workings, however, are confined to the eastern half of the calcareous zone, between Shwenyaungbin (22˚ 55’: 96˚ 19) and Mogok, where the condition of the bands suggests that they have been subjected to a more intense degree of compression than further west, where rubies appear to be absent.
The following accounts of the mines have been published since the district was thrown open by the annexation of Upper Burma in 1886: –
1888-1889. Gordon: Popular accounts of the mines and their surroundings.
1889. Streeter: Account of a visit to the mines, and of the native system of mining.
1895. Barrington Brown and Judd: An exhaustive treatise on the geology and petrology of the district, with a discussion by Prof. Judd of the genesis of the corundum and the minerals associated with it.
1896. Bauer: Describes the mode of occurrence of the ruby and the petrology of the associated rocks and minerals.
1897. Wynne: Notes on the geology of the area and description of the European and native methods of working.
1901. Morgan: Describes the operations of the Ruby Mines Co.
1909. Anon: A brief account of the mines and their development.
1910. Goldschmidt and Schroeder: Describe the crystallographic characters of ruby from Burma.
1915. Claremont: A popular account of the operations of the Ruby Mines Co.
The native workings, as described by Barrington Brown and others, are of three kinds: (a) Loodwin, in which fissures and hollows in the limestone, filled with detritus derived from its disintegration by weathering, are followed up and quarried. (b) Hmyawdwin or cuttings driven into the rain-wash on the hill slopes, covering the outcrop of the limestone; and (c) Twinlone, or pits sunk in the alluvial deposits spread over the floor of the valleys, in order to reach the gem-bearing gravel, called byon, which usually lies at a considerable depth. Small rubies are also obtained by washing the sand and gravel in the beds of streams.
In 1889 a lease of the ruby tracts was granted to the Burma Ruby Mines Co. at an annual rent of Rs. 315,000 plus a share of profits, together with the right to levy royalties on the output of native workings in the townships of Mogok, Kyatpyin, and Katha. The operations of the Company have hitherto been confined to a systematic excavation of the alluvial deposits covering the floor of Mogok valley, which was apparently in former times occupied by a lake, and in washing the byon with the aid of most modern appliances. Electric power is largely used for driving the machinery and is obtained from a waterfall at the outlet of the valley.
In addition to the rubies, the byon contains large quantities of spinel, usually of brilliant red colour, and more rarely sapphires and crystals of blue apatite. Tourmaline is also common but is of the black variety and of no value as a gem.
The crystalline limestones are considered by Judd to have resulted from the decomposition at great depths of the lime felspars contained in basic gneisses and granulites, with a subsequent concentration of a portion of the alumina derived from the aluminous silicates, in the form of corundum. A transitional stage was the formation of scapolite gneisses through the werneritization of the felspars in the original rock. The stratigraphical evidence, on the other hand, seems rather a point to the conclusions arrived at in the case of the similar occurrence of rubies, etc., at Naniazeik, viz., that the limestones were originally calcareous sediments, and that they have been altered by contact with igneous intrusions under conditions of great pressure.
Sapphire
The rubies of Upper Burma are invariably accompanied by sapphire, derived in the same manner from crystalline limestone. The proportion of blue corundum found in the gem gravels is usually much smaller than that of the red variety, though the stones are often of larger size.
References: La Touche T. H. D. (1918): A Bibliography of Indian Geology and Physical Geography with an Annotated Index of Minerals of Economic Value.
Jadestone
Myitkyina. Tawmaw (25˚ 42 ‘: 96˚ 17’). The mineral jadeite, a silicate of soda and alumina, has been worked for an unknown period in this locality and in the neighbourhood, mainly for export to China, where it is highly prized on account of its supposed magical qualities. The earliest description of the mines was published by Griffith in 1847. The stone, he says, is found in rounded boulders embedded in yellow or orange-coloured clay, and is extracted from pits not more than 20 feet deep. The revenue derived from the mines in 1836, the year previous to his visit, is said to have been about Rs40,000. The mines are also mentioned by Hannay but he does not appear to have visited them.
After the annexation of Upper Burma, the mines were visited and described by Noetling, who observed that in addition to the boulder deposits seen by Griffith, jadeite had been discovered in situ a dark-coloured serpentinous rock, intrusive in Tertiary (probably upper Miocene) sandstones, and clays.
More recently (1907) a full description of the geology of the area, and of the mode of occurrence of the jadeite, with remarks on the petrology of the rocks associated with it, has been given by Bleeck. The mineral is shown to occur as a compound dyke, consisting of jadeite and albite with an outer border of amphibolite, intruded into serpentine under conditions of high compression. The jadeite occupies the centre of the dyke, and is of pure white colour, with included green patches of varying shades, which are the portions sought for.
Boulders of jadeite are also quarried from Tertiary conglomerates at Hweka (25˚ 29’: 96˚20’) and from the alluvial deposits of the Uru (Uyu) River near Mamon (25˚ 36’: 96˚ 18’). Their occurrence in the Tertiary beds proves as Bleeck points out, that jadeite intrusions belong to a far earlier period than that assigned to them by Noetling.
The mineralogical characteristics of the jadeite of Tawmaw, and the rocks associated with it, have been discussed by Bauer, Krenner, and Fischer. Analysis of the mineral has been published by Damour, Farrington, and White (1922). The average annual production of jadeite in Upper Burma, from five years 1909 to 1913, amounted to 2,109 hundredweight. In 1914 and 1915 the amounts produced were 3,764 cwt and 3,692 cwt respectively.
References: La Touche T. H. D., 1918: A Bibliography of Indian Geology and Physical Geography with an Annotated Index of Minerals of Economic Value.
