Burma
By far the most important source of fine rubies and sapphires is the region around Mogok, in upper Burma. Mogok is situated east of the Irrawaddy River, approximately ninety miles northeast of the city of Mandalay. The valley in which Mogok is located is approximately twenty miles long and two miles wide. The most widely exploited deposits are within an eight mile radius of the town, but some mining continues as far north as Momeik, twenty-eight miles to the north, as well as sixty miles to west, at the villages of Twingwe and Thabeikian, on the Irrawaddy.
Mogok is in an area of heavy rainfall, usually from 100 to 135 inches annually, and is at an elevation of approximately 4000 feet. It has a population of about 150,000 almost all of whom are engaged in one way or another in gem mining and/or cutting. It is in an area of ancient crystalline rock, including a number of schists of different types, some of which are traversed by large pegmatite dikes. There is also an extensive body of marble, portions of which are the result of contact metamorphic activity. The combination of pegmatite dikes contact metamorphism and the replacement type of deposits in the marble or limestone gives the Mogok area a most amazing assemblage of minerals, probably as many species as in any other area of similar size in the world. No other region has such a wealth of gem minerals. Of course, the most important of these is the corundum family.
Mining has been carried on the Mogok area for many centuries. Rubies had been mined there prior to the agreement in 1245 A.D. between the King of Ava and the local ruler of Momeik. Until 1888, shortly after the annexation of Burma by Britain, the mines were worked by native laborers. In 1988 or 1889, they were taken over by the Burma Ruby Mines, Ltd, an English company. Evidentially, this company found that the richest deposits were partly beneath the town of Mogok. As a town result, it became necessary to relocate the town in order to mine the site. This former mining area today is marked by a rather large lake. Burma Ruby Mines, Ltd continued to operate the deposits through many vicissitudes, finally closing them in the middle of the Depression, in 1931.
The first contract signed by the Company with the British Government called for a 40,000 rupee annual fee ($144,000), plus one sixth of all the profits obtained. This contract, which was for a period of five years, expire in 1895. During the period of the first contract profits were excellent. Among others a ruby was mined that was purportedly sold for the equivalent of $100,000 an enormous sum in the late nineteenth century. The next contract called for a tax of about $800,000 plus one fifth of the total profits for the fourteen year period. All of the mines in the area were covered by the contract.
As the main mining operation deepened and extended, water became an increasingly serious problem because of the heavy rainfall. During the rainy season, mining became impossible; as a result, efforts were made to draw the water off through tunnels. This provided only a temporary solution, even though large sums were expended in constructing the tunnels. In addition, the company suffered materially from high grading, a form of pilferage that seems to be a feature of most mining where the material sought is very valuable.
From 1914 through 1922, the expiration date of the third contract, there were some serious problems. The main operation continued until 1922, despite fairly large losses in the interim. After that time for several more years, some company representatives worked the mines with local people on a half share basis. The mines were given a new lease on life by the increased interest in gem corundum caused by the sudden popularity of star sapphires and rubies. However, mining ceased and the company did not operate after the Depression year of 1931. Since that time, the area has been worked by small operators. The late Martin Ehrmann, a Los Angeles colored stone dealer, wrote in Gems & Gemology that in the late 1950's there were about 1200 small mines operated by individuals and small groups. These were mostly one to three man operations, but Ehramann stated that others employed as many as fifty miners. He reported that high grading was held to a minimum by making all the miners shareholders on a small percentage. This, of course, would not eliminate all pilferage, but might reduce it materially.
The present primitive form of mining usually calls for the removal of an overburden that has a depth of as much as fifteen feet over the gem bearing gravels. In large operations, the overburden is removed from an area of considerable size. Usually, actual work on the mining of the gravels does not begin until rather large sections of over burden have been removed. In a typical recovery operation, the first step is to move the larger boulders to the sides and then transport the gravels to a concentrating area. First, the dry material is sifted through a series of wire mesh sieves: the largest stones are removed at the highest point, the middle-sized ones at the second, and the smallest size large enough to warrant careful treat merit at the third level. The operation of washing the concentrates and discarding the lighter, worthless material, which is similar to panning gold, is accomplished after segregation by size. Another washing method consists of placing the valuable gravels in a wooden flume with running water, in which they move several feet before falling over a small waterfall. At the end of the fall the miners catch the gravels in baskets and shake them to remove the residue. The gravels not caught at this point travel over several more falls, under which are held additional baskets.
Next the concentrates are picked over by hand to remove the gemstones. Usually, the mine owner does the picking; he may or may not be assisted by one or more men it depending on the size of the mine. The usual process is to move the gravel with some kind of tool held in one hand and pick out the gemstones with the other. These are placed in a bamboo container as the gravels that have been examined are pushed off the table. Since the gravel that has been removed may still contain small pieces of gem material that the owners does not consider worth saving or that have been overlooked, there is still some sorting that could be done by low priced labor. This material is usually sold for a very low price to women relatives of the mine owner for further sorting.
Small operations are usually conducted by removing the overburden in very small sections, usually in an area about twenty to thirty feet square. Such small pits have to be shored up carefully with bamboo. A small winch is used to carry rattan baskets of gem gravel to the surface, where it is washed and sorted in a manner similar to that used in a larger mine. Presently, the Burmese government is updating its mining operations and since 1973 has had an extensive prospecting program looking for new deposits.
Because of the method of marketing, reliable figures for the ruby and sapphire production of Burma are impossible to obtain. In the days of the Burma Ruby Mines company, this was a less difficult problem, but since that time it has been possible to judge only on the basis of the number of people engaged in mining. Even this does not lead to too much information, since their success varies widely. It is difficult in a town such as Mogok to determine relative affluence. Many of the well-to-do people give little evidence of their economic status. The impression today is that there are more natives engaged in mining in the Mogok area than in Ceylon and many more than in Thailand or Cambodia; no actual figures can be quoted to support this impression, however.
Fine corundum appears to be constantly in short supply, a situation that is unlikely to be alleviated in the foreseeable future. The discovery of rich new deposits is always a possibility, but because the river gravels and exposed mountainous areas have been inspected so thoroughly in the search for gold, it would seem that the easily located gem deposits would have been found by now. However, improvements in prospecting methods may change the picture overnight.
Sri Lanka (formerly Ceylon)
Sri Lanka, which was previously called Ceylon, is one of the most important gem sources areas in the world, and since the term Ceylon is well established in the trade and literature, it will be used interchangeably in the course with Sri Lanka.
Most of the mining activities of Sri Lanka are concentrated in the southwestern part of the island about the city of Ratnapura, which is a Sinhalese word meaning "city of gems". As in Burma, mining today is carried on by the native population, usually in very small operations. The mining methods are very similar to those in Burma.
As with the alluvial deposits, the beds often are not contiguous but may be found in lenses, or pockets; sometimes, however, they are in fairly extensive beds. Most of these are buried in some depth beneath the present surface, at any point down to bedrock , Usually, the bedrock is within one hundred feet of the surface; often the gem minerals are much closer to the surface than that. In general, the production tends towards distinctly paler stones than those produced in Burma. The Ceylon corundum is noted more particularly for sapphire than for ruby, but both are more likely to be light in tone than their Burma counterparts. The blue sapphire recovery, however, does contain some excellent dark stones. In addition, the Ceylon gravels are noted for fancy sapphires, including all of the colors except brown and blacks.
The richest locality for ruby and sapphire mining in Ceylon is the Saffragam district, on the southern slopes of the mountains of that name. Stones are distributed widely in alluvial deposits on the western plain between Adam's Peak and the sea; from north of Kandy to the southern tip of the island, near Matara; in the valley of the Kalany Ganga River, a few miles east of Colombo, the capital; and in river beds on the Mohagam River and its tributaries; which flow from the mountainous centre of the island to the south-east coast. The sapphire and garnet seem to have come from gneisses, whereas ruby, spinel and a number of together gemstones come from marbles associated with the gneiss. However, as in most gem mining areas, the process of weathering and erosion has concentrated the gem minerals in the alluvium to such an extent that the gravels become profitable to mine, whereas the original deposits are too poor to be worked at a profit.
Thailand (formerly Siam)
Rubies and sapphires of various colors come from Thailand, near the border of Cambodia (Khmer Republic). On the average, the rubies are fairly dark purple-red to brownish red and more closely resemble pyrope garnet than rubies from Burma. On the other hand, Siamese sapphires, although usually dark, occasionally reach a very high-quality. The mining area, which is in a region centered around Chanthaburi, includes several districts; one of these is Bo Pie Rin, in Battambang. This area produces a significant share of the sapphires that are available to jewelers. Since the Chanthaburi area is famed for its sapphires, and for many years Burma was not supposed to produce fine qualities, there is reason to believe that many Burmese sapphires were shipped to Chanthaburi and sold from there with the implication that they were of Siamese origin. Stones from Cambodia were also included with the Chanthaburi production. This area produces many brown and black sapphires, being well known as a source of the presently quite popular black star sapphires. The Cambodia source is in the gem gravels of the Pail in river, a tributary of the Nammong River, where sapphires occur with zircon and ruby. In these areas making up the Thailand group of mines, a small but significant number of green sapphires is found: however, as elsewhere, they are rare.
There was a time when Battambang was the most important sapphire source in the world. It was estimated at about the turn of the century to be yielding approximately five/eights of the total world production; moreover, the stones were the finest available from any source. Battambang, which was at that time a part of Siam, is now a portion of Cambodia, one of the three nations into which French Indo-China was divided following the French defeat in the mid-1950's. An idea of the importance of early Siamese production, even by today's inflated currencies, may be gained by noting that the sales of a single firm of London gem merchants in 1889 amounted to 75,000 pounds sterling ($375,000), according to Streeter, a prominent British gem writer of the period, Considering the relationship between the value of a dollar in 1889 and today, and that annual United States imports of rough and cut natural colored stones total less than $5,000,000, this figure for one variety from one source is staggering.
The Battambang sapphire production is from a slightly sandy clay that is usually found just a foot or two beneath the surface, particularly on the sides and floor of the Phelin Valley. Apparently, the deposit has been traced over an area of at least one hundred square miles. Rubies come principally from the Thailand provinces of Chanthaburi and Kraft, although a few are also found in the sapphire mines of Battambang.
India
One of the most famous corundum deposits is high in the Vale of Cashmere, or Kashmir (formerly Cashmere), in the Zanskar Range of the Himalayas. Here rich blue sapphires have been found in pegmatite. Other minerals found at this point include garnet, tourmaline and euclase. The high elevation of the deposit restricts the period at which it could be mined to just a few months a year. Apparently, the Kashmir sapphire deposit has not been a long-term source of fine stones. It seems that it was mined rather extensively from about 1861 or 1862 for a period of perhaps forty or fifty years. Recently, production, if any, has been limited. The deposit is located in, a small upland valley in the district of Padar, a number of days, journey southeast of Srinagar, the capital of Kashmir. It is near the village of Soomjam, which is the highest of the villages on the southwestern slopes of the high Zanskar Range. The sapphires are found in a valley about one thousand yards long and four hundred yards wide; at its lower end, it has an elevation of approximately 13,200 feet above sea level and rises toward the northwest at a very steep angle. The first discovery was supposed to have been made in a sapphire bearing rock that formed a precipice at the head of the valley. A landslide exposed the rock, which is at an altitude of almost 15,000 feet, near the lower limit of perpetual snow early in the exploitation a large number of stones were mined from this rock. Shortly thereafter, however, the discovery of sapphires on the valley floor in the loose rock that had been weathered from the primary deposit changed the picture. This soon became the chief area of mining, for the aluvium was much richer than the sapphire bearing rock. In this area, micaschists and garnet-bearing gneisses are inter foliated with marbles resulting from contact metamorphism. The sapphires are found in stringers, or veinlets, of franitic composition that penetrate the contact marble and are accompanied by abundant dark-brown tourmaline. The deposits, which accumulated from weathered material from the original source, form a whitish band of clayey material in which the sapphires are found. In the early days of mining, shortly after the discovery, the stones were so numerous and were obtained so easily that they were gathered in great numbers. The stone dealers of major Indian cities to the north evidently thought they were less valuable stones and purchased them very cheaply. Apparently, their abundance decidedly affected the market for a short period, but the Maharajah of Kashmir intervened and permitted mining only by licensed persons.
Most of the stones recovered are blue, bluish white or bluish gray. It is common to find crystals with a difference of color in different portions. Most of the stones are cloudy and fine gem material occurs rarely; however, the finest material is magnificent. It is apparent that the mines are now being worked very little, if it all. Whether this is because they are exhausted or due to the rigorous conditions under which the miners must work is not known. Whether it is still possible to mine the original primary deposit in hard rock is not known, but it would appear that it would have been difficult to exhaust it quickly in the few months of the year in which mining by the rather primitive methods could have been carried on. It is possible, however, that the primary deposit is not sufficient rich to justify exploitation, even at today's prices.
A very low quality of dark-purple sapphire, which is highly laminated and sold as "star ruby" comes from else were in India.
Some rubies have been found in the Badakshan district of Afghanistan; here are the ancient mines that supplied the rubies for earlier civilizations. Another small deposit is near Jagdalak, thirty-two miles east of Kabul, where the rubies are found in micaceous marble. The Badakshan deposit is on the Oxus River, not far from the lapis-lazuli mines described in an earlier assignment. It is in the district of Shignan, about thirty seven degrees north latitude and seventy one and one half degrees east longitude. The mines lie between the axis and its tributary, the Turt, near Gharan, sixteen miles below the town of Barshar in the lower foothills. Little is known of this deposit, except for the fact that it was important in the time of Marco Polo.
Australia
Corundum has come from several areas. The Inverell district of New South Wales is the most important source of alluvial gem corundum about 150 people are involved in the mining operations. Over $ 4,000,000 worth of sapphires were produced in the Inverell area in 1975. Green sapphire has been found in Victoria. Another older area of importance is a region of 200 square miles near Anakie, in Queensland. Near the towns of Rubyvale and Sapphire are situated a group of several prospects operated by approximately 200 workers. Other prospects are on the central railway at the station of Willows and along the creek and ridges of the area where a 217 1/2 carat yellow sapphire was found in 1946. The production of Anakie has been almost entirely sapphires, with a wide range of colors. The blue stones are usually too inky and dark to be of much value; however, black stars and a number of other colors, especially yellow, have been recovered and used in increasing quantities in recent years.
North America
Gem corundum is found in two areas in the United States. There are two sources in Macon County, in the southeastern portion of North Carolina. In one of these rubies are found on Corundum Hill at the Lucas Mine, where a body of serpentine, which forms the main mass of this hill, is traversed by large veins of common corundum. In some of these veins, almost transparent material is found, some of which is sufficiently transparent to be cut-able commercially. However, rubies of much better quality have been found at Cowee Creek, about five miles from Franklin in the same county. At this location, small tabular crystals and short prismatic crystals are found in garnet bearing basic rocks; some have the color and transparency of fine ruby. Although most of the stones are rather heavily flawed, some comparatively flawless ones are occasionally recovered.
The other source in America (again two distinct localities within the same general area) is in Montana. Here a number of sapphire bearing alluvial deposits have been found in the upper Missouri River, not far from Helena. In this occurrence, the sapphires were recovered as a by-product in gold-mining operations. The crystals and grains were very small, usually from one-quarter to one-half inch in diameter ,and quite light in color.
The most important corundum deposit on the North American continent is at Yogo Gulch in Fergus County, Montana, at a point between seventy-five and one hundered miles east of the Missouri River deposit. This deposit is a basic igneous dike, called a shonkinite, in which the corundum occurs as disseminated crystals and gains that seldom exceed a size from which three or four carat stones can be cut. Most of the material is much smaller than that, being most suitable for calibre purposes. The photographs below shows a portion of the sapphire-bearing dike that was cut away during the early years of the mine's operation. It is approximately five miles long on the surface, dips nearly vertically, and the average width is about eight feet.
As mentioned previously, the mine was worked originally by a British firm, the New Mine Sapphire Syndicate, from 1895 to 1930. It was operated intermittently by leasers until acquired in 1968 by Sapphire International Corporation. Since that time, the mine has been actively developed, very fine blue stones, comparable to the best Burmese product, are being recovered, as well as some of a slightly paler blue color. They are bringing prices comparable to and not far below those of top-quality Burmese stones. A small percentage of the recovery is of the fancy type, principally purple, violet, and grayish green.
The ore is produced from an adit and from slopes above the adit. This mined ore is hauled by tram to the mill located close to the adit. The milling process is simple and makes a good recovery. It consists of screening and washing the dike material and subsequently recovery of the freed sapphires by jigging. The plant capacity is about 24 tones of crude ore per hour with about 75% mining recovery. Probable ore reserves will last several years. Production in 1973-74 was 11 carats/ton. About 58,000 carats were produced in 1974, which when cut brought $400,000 on the world market. Reportedly, the mine was sold in 1976 to an unidentified group in San Francisco.
Africa
Sapphires of various colors occur in Africa, and earlier deposits were once found in Namaqualand and the Transvaal. Large ruby crystals were discovered in Tanzania about 1952. Sapphires of many colors have recently been mined in the Umba River Valley, in Tanga Province, and near Morogoro in Tanzania.
What was described as "the world's richest ruby mine" was staked out in 1974 by geologist John Saul and his partner Elliott Miller, in Tsavo West National Park, Kenya. Unfortunately, in 1975 the mine was taken over by government officials and last reports indicate negotiations were in process and a settlement near. Facetable corundum also occurs in Rhodesia and Southern Malawi. Rubies are being mined at Chimwadzulu on the northwest shore of Lake Malawi.
