Corundum, Rubies, Sapphire




Ruby Sapphire

Ruby

The price of wisdom is above rubies; so said Job in the Bible, implying that even then this red variety of the corundum species was extraordinarily valuable and highly esteemed. The superlative that have been used to describe ruby and to praise its virtues are seemingly without end. In Sanskrit, it had many names, all of which showed clearly that this stone was more valued by the Hindus than any other; "ratnaraj" (king of precious stones), "ratnanayaka" (leader of precious stones) and "padmaraga" (red as the lotus) were just a few of the many complimentary terms applied to corundum.

The word corundum (pronounced ko-RUN-dum) came to us through the French "corindon" from the old Hindu word korund. Ruby is from the Latin "ruber" meaning red.

A multitude of legends and strange beliefs surrounded the ruby in ancient times. Among, other things; it was thought that the wearer of a ruby was blessed with health, wealth, wisdom and outstanding success in affairs of the heart. Further, he acquired the magic ability to live in peace with his enemies, provided a ruby ring was worn on the left hand or a ruby brooch on the left side. Early Romans included it with other red stones under the name carbunculus, and Pliny said that these stones were easy to counterfeit by the art and skill of the Lapidaries, who put a foil beneath them to make them brilliant and glitter like firer. He also reported that by steeping these dark and dusty stones in vinegar for fourteen days, they would become pure and lively and remain so for fourteen months. Moreover, they were imitated in glass, according to Pliny, and at first sight they were excellent, but by grinding in a mill, the fraud can be immediately discovered, as is true of any other artificial or false stone.

The Bible tells us that the ruby represented the tribe of Judah. Aaron's breastplate contained for its fourth stone what was called snopek, which may have been either garnet or ruby. On this stone was carved the name of Judah. This noble gem has always been a favorite adornment for royal crowns, and from Judah sprang the royalty of Israel.

For centuries, the Hindus believed that white (colorless) sapphire was an "unripe" ruby that would eventually mature. The Burmese gem miners held that pale-colored rubies, if buried in the earth, would gradually change to a fine red. To them, ruby was the fully ripened member of the corundum family. To the Ceylonese miner, flawed stones were "overripe". Garcias Orta, who traveled in India from 1534 to 1570, said that the color of the ruby increased as the stone ripened. Von Linschoten, another early writer, said of the color, "The cause whereof is because that in the rockies and hills where they grow their first color is white but by force of the sunne they are in time brought to their perfection and ripeness as rubies" but wanting somewhat of their perfection and being dig out before that time, they are of divers colors, as I said before, and how much paler they are and lesser red.

The Burmese had an old legend telling of the "blazing red" stones in a "bottomless" valley. Natives threw pieces of meat into the valley to lure vultures, in the hope that some stones would cling to the meat, to be recovered by killing the vultures.

Even in the last few hundred years many believed, in the therapeutic action of rubies and other gemstones. Sir Robert Boyle, the English physicist, writing in 1663 attempted to show that the medicinal action of gems was not compatible with observed facts. He said: "I am not a altogether of their mind that absolutely reject the internal use of leaf gold, rubies, sapphires, emeralds and other gems as things that are unconquerable by the heat of the stomach". In a 1757 price list of a German druggist, all of the precious stones used for healing appear. Ruby was one thaler (Rs. 6000), which indicates clearly the quality of ruby offered for sale. Naharari, a physician of Cashmere, who wrote in Sanskrit of the medicine of the thirteenth century, said, "Ruby is a valuable remedy for biliousness and flatulency". A famous ruby elixir was compounded by a secret process at great expense, and was used only by wealthy patients. The ancient method of applying it as a cure was to place it on the tongue, which was at once rendered cold and heavy, so that only incoherent sounds could be emitted. The fingers and toes also became cold and a violent shivering followed. Thus, the bad symptoms disappeared and a sense of (elasticity and well being followed the cure was completed. The stone was also used as a disinfectant in dread diseases.

Ruby was valued not only by the Burmese for its beauty, but because it was thought to confer invulnerability. To exert this power, however, the stone had to be inserted in the owner's flesh through an intentional would. It was said that a soldier or warrior who voluntarily suffered such pain and inconvenience would be immune to sword, spear and gun. Francesco Petrarch, the noted Italian poet of the Middle Ages, tells of a ruby ring worn by John II, of France that was supposed to possess talismanic powers. However, it did not preserve the King from defeat, for he was made prisoner at the Battle of Poitier in 1356. Year's later, after John had been taken to England, the ruby was returned to him, enabling him again to see an object of infinite value and beauty but of no use whatever.

In the Royal Collection of England there is a gold ring set with a pale but comparatively flawless ruby into which is carbed a portrait of Louis XII, of France. This work is believed to have been executed during the lifetime of the king by Domenico die Camei, famous Renaissance gem cutter who also engraved a portrait of the Milanese Duke Ludovico Sforza on a ruby, According to C.W. King, a historian of carved engraved gems, it is the earliest Renaissance portrait cut on a stone of such great hardness.

When in 1360, the Earl of Richmond married the Lady Blanche, daughter of the Duke of Lancaster, King Edward III gave as presents a ruby ring and belt set with rubies, emeralds and pearls. The rubies may have been considered especially appropriate, since the red rose was the emblem of the House of Lancaster.

The coronation ring of the English kings is of pure gold and is usually set with a large tablet-cut ruby of a violetish hue on which the figure of St. George's cross is engraved. Around the ruby are set twenty-six diamonds. Although the queen consort is also given a ruby ring it is not engraved. However, surrounding the ruby are sixteen smaller rubles that are graded for size in such a way that the largest are placed nearest the central stone and the size diminishing as the distance increases. These rings are placed on the fourth finger of the king and queen. The St. George's cross on the coronation ring of William IV was formed of five rubles: a square central stone and four oblong ones for the arms of the cross.

Large gem quality rubies have always been uncommon; therefore, only a few specimens have gained historical importance. They were even more rare in the early days of Burmese mining, when those that were found were jealously hoarded by the rulers of that country. When describing a ruby, a storyteller's imagination knew no bounds. According to the Arabian Nights, for example, Sinbad the Sailor saw a cup of ruby a span high. Marco Polo wrote in the thirteenth century that a Singhalese monarch owned a red gem four inches long and as thick as a finger, for which Kublai Khan, the Emperor of China, offered the value of a city.The Singhalese ruler refused, saying "If all the treasures of the world were laid at my feet, I would not part with this jewel". About two hundred years later, Sir John Mandeville wrote a book of travel stories, but it is doubtful whether they were true experience. In one of them, a ruby owned by an Fastern king was described as a foot long and five fingers wide. No gem expert has ever examined literature. If such stones actually existed, they probably were garnets or tourmalines or were nontransparent. A number of magnificent stones, however, are on view in various museums and collations around the world. A 167 carat translucent crystal of fine color, called the Edwards Ruby, may be seen in the British Museum of Natural History. The American Museum of Natural History displays one of the largest star rubies in existence; the 100 carat Edith Haggin de Long Star Ruby (see photo). Both of these institutions also own a number of smaller top quality stones.

Sapphire

Sapphire, the traditional birthstone for September, is derived from the Latin word "sapphirus". meaning blue. When first used, it denoted lapis-lazuli and possibly other opaque minerals that were blue in color. As it is with ruby, the legendary virtues ascribed to a sapphire are manifold. It was the royal gem to protect kings and potentates against harm and envy. It was regarded as the best stone for ecclesiastical rings. Tradition tells us that it was on a sapphire that the Ten Commandments were engraved. The Persians believed that the earth rested on a great sapphire, the color of which was reflected to give the sky its blue color. Also, it was long considered the symbol of truth and constancy. Although many of the original descriptions of sapphire alluded to lapis-lazuli, the legendary attributes came to be applied to our present-day sapphire.

Sapphire, as well as ruby, was thought to have a strong medicinal powers. One ancient writer on this subject says that "the figure of a ram or a bearded man engraved on a sapphire has the power to cure a person from many ailments and to free him from poison and demons". At one time, it was credited with the power to remove all impurities and foreign matter from the eyes. Charles IV used an oval, oriental sapphire for touching the eye. Von Helmont, a German observer of the period, is quoted as saying "sapphires are to cure boils, and have a magnetic force that attracts all poisons". Among the gifts offered at St. Paul's in London in 1391 was a sapphire given by a generous bene factory who stipulated that it should be kept at the shrine of St. Erkenwald to cure eye diseases, and that a proclamation should be made of its remedial virtues.

Star sapphire, called "the stone of destiny", had superstitions of its own. The three chatoyant bands that form the star represented faith, hope and charity. Oriental tradition reveals it as a guiding gem, warding off evil omen and bringing good fortune to its owner, even after the gem had passed from his hands. Sir Richard Burton, the famous explorer of the last century and a translator of the Arabian Nights, owned a large star sapphire that he considered his talisman because it brought good horses and prompt services wherever he went. The reward for such a service was a view of the stone, and the Orientals believed that good luck was sure to follow.

There are probably more fine specimens of the various colors of sapphire on display than of ruby. The American Museum, for example, has the spectacular 563-carat Star of India, one of the world's largest (light-colored stone in accompanying photo). Although it is somewhat pale in color, it is remarkable for the perfection of its star and its almost complete lack of flaws. It is cut with a very deep back and actually shows an almost equally fine star on the reverse side. Another outstanding, specimen is the 116.75 carat Midnight Star a deep-violet stone of fair quality. This museum has in addition, excellent examples of faceted yellow, green and other colors of sapphire, many of which weigh between one hundred and two hundred carats; its 100 carat orange: (padparadscha) specimen is the finest of its kind on display in the United States. In the Imperial State Crown of the British Regalia are two historical stones. One of these is called St. Edward's Sapphire, a rose-cut stone of good color. The other is the Stuart Sapphire, also described as a stone of fine color which measures one and one-half inches in length and one inch in breadth. The now famous Black Star of Queens land, found in Australia in 1948 is the largest asteriated corundum of any color ever reported. Weighing 1156 carats in the rough, it weighed 733 carats after cutting and measured 2 3/16 x 1 27/32 x 1 1/32 inches. It is oval in shape and bout the size of the hen's egg. The stone is privately owned by a firm of gem dealers in Los Angeles.

Varieties of Corundum, Rubies, Sapphire

Corundum is one of the fairly common minerals in the earth's crust. It is found in many different kinds of rock and in many places on the earth's surface, but only under the rare occurrence of nearly ideal conditions is transparent material formed. With the exception of black star sapphire, only the transparent to translucent varieties are classed as gemstones.

Ruby

Only transparent corundum of medium light to dark tones of red to purple-red hues is properly called ruby. Very light tones of red are correctly called pink sapphire. Even some stones that are light rather than very light in tone are properly called pink sapphire. A very intense red color is necessary to justify the use of the term ruby.

On the basis of the usual product of certain ruby-producing countries, several terms are used in the American jewelry industry to describe different colors of ruby. There is too little consistency in trade grades to suggest that any stones meeting these descriptions will always, or even almost always, be described by the appropriate term. The trade grades listed below are included so that the student will understand their usual meaning, rather than as a recommendation that they be employed.

Burma, Burmese or Oriental Ruby

The finest blood-red rubies ("pigeon's-blood" ruby is the term often applied to the finest) are called Burma rubies, despite the fact that some very dark and some pale-colored stones also come from Burma. In some cases, the word Oriental is used to describe a ruby of fine quality; but since all three of the major ruby sources are in the Orient, the use of this term is more confusing than helpful. In Europe, it tends to be used for stones that are called Burma rubies in this country. Two somewhat less desirable subdivisions of this fine color are "beef-blood" rubies (slightly darker tones of red) and "French-color" or "cherry" rubies (slightly lighter than a so-called blood red).

There is no doubt that the finest rubies are found almost exclusively in Burma; however, there are also Burmese rubies that are lower in quality than some of those found elsewhere. If terms such as Burma ruby are to be used for trade: grades, they should be applied only on the basis of quality, regardless: of source. Thus, even though a stone comes from Burma, if it is light in tone and more nearly a pink sapphire than a ruby, it should not be called a Burma ruby, regardless of its origin. Some rubies from Thailand and some from Tanzania have the beauty associated with the good Burma qualities.

Siam, or Siamese, Ruby

This term is still used, despite the fact that the country of origin is now called Thailand. The usual output from the Thailand mines is dark red to brownish red, sometimes resembling almandite or pyrope garnet. These stones are rarely of a quality that even approaches that of fine Burma stones. They are distinctly less desirable. However, not all Thai rubies are dark or brownish. Some from nearby Pa Hill, Cambodia, and also from other mines in Thailand are bright and very desirable.

Ceylon Ruby

Light to very light red or purplish-red stones are mined in Sri Lanka, formerly Ceylon. Those that are medium light in tone (i.e., not light to very light), so that they may appropriately be classed as ruby, are called Ceylon rubies. The light to very light red, of course, should be called pink sapphire. Because of their lighter tone, these stones are usually more brilliant than Burmese or Siamese stones. Fine stones from Sri Lanka usually bring higher prices than the better qualities from Thailand.

African Ruby

Some good quality purplish-red (pigeon's-blood) faceting grade ruby occurs at Longido and Lossogonoi, Tanzania; however, the material appears to be sheet like and melee size stones are the major production. Some excellent quality ruby of large size, up to 8 carats faceted, has come out of Tsavo National Park, Kenya. Good cabochon ruby is also reportedly found in northern Kenya along the Tana River.

Star Ruby

Stones that have a ruby color and that also display a distinct asterism when cut in cabochon are called star rubies. The tendency is to allow more latitude in color when applying the term ruby to stars than is true with faceted stones. In other words, stones that do not have a true ruby color (e.g. those that are too pale or too purple) are sometimes passed off as star rubies. The only justification for a difference in color stands in this regard is that standards the "silk" in asteriated stones makes them slightly less transparent and tends to gray the color and lighten it. A cat's-eye effect has also been encountered in ruby but it is exceedingly rare, especially in a sharply defined band.

Sapphire

Since the term sapphire is applied accurately to all colors of corundum other than medium light to dark tones of red to purple-red it is best to use a color prefix for the various colors of sapphire other than blue. Sapphire used alone means the blue variety to laymen and jewelers alike. Blue sapphire is also divided into trade grades in the jewelry industry, but these grades are not as clearly based on the usual output or the better quality output of the important present or former sources of sapphires, as are the trade grades of ruby. Since there are more sapphire mines producing fine qualities than is true of ruby mines, the locality names associated with sapphire trade grades are less meaningful and less consistent. The trade grades of blue sapphire are as follows:

Kashmir or Cashmere Sapphire

Kashmir sapphires are encountered today, even though the mines in that area are not presently being worked, nor have they been worked for a number of years. The term is applied to velvety violetish-blue stones (so-called cornflower blue) that are not exceedingly transparent; this lack of transparency produces a "sleepy" appearance, unlike that of other blue sapphires. Although the term Kashmir has persisted for many years and the implication is that such sapphires are not longer found, this is not true, since occasional stones mined in Burma and Thailand have the same appearance as the Kashmir grade. Actually, a significant percentage of the product of the Kashmir mines, when they were operated, was paler but more brilliant than the finest stones. Magnificent sapphires are found in Montana, Thailand and even in Australia, so trade grades need have no bearing on source.

Burma or Oriental Sapphire

This term is used in the American trade for a very fine quality. It has been described as a fine "rich" blue or "royal' blue (slightly violetish blue). The distinction between the Burma stones lose some of their color and appears somewhat inky under artificial light.

Siam or Siamese Sapphire.

This term is used to describe very dark blue stones. Since they seem to be exceedingly dark, even in daylight, they might appropriately be called almost blue-black in color. In England, the term Siam sapphire has been used to indicate a stone ranking next to Kashmir in grade: an intense dark blue with a slightly velvety body appearance. Although it is not used for that type of stone in American, the description does cover some of the fine stones mined in Thailand. The American trade-grade description, however, applies to a poor grade.

Ceylon Sapphire

This term is usually applied to pale grayish-blue to light blue-violet and fairly brilliant stones. Some stones contain a considerable amount of silk, which reduces brilliancy and may impart a grayish color. Blue Ceylon sapphires are somewhat subject to unevenness of color. Fine sapphires from Sri Lanka are among the finest.

Montana Sapphire

Since the two producing regions in Montana (described under Sources and Recovery Methods) yield, or yielded, distinctly different types of sapphires, the term Montana has little relevancy. It actually described the alluvial production more accurately than the output from in place deposits in Yogo Gulch. The alluvial production is mostly light in color. The blue stones have been described as an electric or 'steel' blue and were highly transparent. Such stones are said to have a "metallic" bluster, which means little or nothing, except that they perhaps give the impression of a higher luster than the; softer appearing, velvety blues from other sources. The term "new-mine" sapphire, which is heard occasionally in the trade, is derived from the New Mine Syndicate, the British concern that owned and operated the Yoqo property prior to 1929. This term was applied to the darker stones among those produced from that deposit.

African Sapphire

African sapphires occur in a variety of pastel colors: pale blue, blue violet, red violet, pale yellow, pale orange, steel-gray and dark brownish orange from the Umba gravels. Some African sapphires exhibit an alexandrite like color change, especially from the Umba River area where some change from steel-blue to a green or to purple. Various colors of pale sapphires and rubies are also found in southern Malawi.

Australian Sapphire

Stones from Australia are commonly very dark and inky and are usually characterized by strong green to very dark violet blue dichroism. Stones of this grade are not necessarily confined, to Australia, but are found also in Siam and elsewhere. Dark feathers and strong color zoning are common in Australian corundum.

Fancy Sapphire

Most of the stones other than blue are called fancy sapphires; however, they are often referred to simply as green sapphire, yellow sapphire, etc. Almost all of the colors other than blue are represented. The majority of those seen in the trade originate in Ceylon.

Yellow sapphire

Yellow sapphire, which is usually referred to as golden sapphire, is a fairly important gemstone. It usually occurs in slightly brownish-yellow colors in light to medium-dark tones. Intense golden yellow, which is rather highly prized, was once referred to Widely as "Oriental topaz", "King topaz" or "imperial topaz".

Intense Orange to Orange-Red

Among the fancy sapphires, stones of these colors are rare and highly prized and considered by many connoisseurs to be among the most beautiful of all gemstones. The intense light reddish orange stones are often called padparadscha (pad-par-AHD-shah) or padparadscha sapphires. The color resembles that of the lotus. Note that dark brownish-orange stones from the Umba River in Tanzania should not be called padparadscha. The orange-red stones are sometimes called bhyacinth sapphires. Both colors find willing buyers in Ceylon itself and these stones rarely enter the foreign trade.

Green Sapphire

Most of the sapphires sold as green are inky stones of the blue Australian or Siamese types that have been cut to display the green rather than the dark-blue dichroic color. When a lighter green stone occurs, it is very attractive and has a certain amount of demand; however, it is too uncommon to be an important stones. It has often been incorrectly called "Oriental emerald" although the color can hardly be compared to that of emerald.

Violet to Purplish Violet

Stones that have a violet or purplish-violet color are usually referred to as amethystine sapphire or, incorrectly, as "Oriental amethyst". Reddish-purpose stones are more frequency called plum sapphires, rather than amethystine sapphires. Some dealers refer to plum-colored stones as "rubies".

Pink, or Rose Sapphire

Light-red sapphires (i.e. stones that are too light in tone to be called ruby) are usually referred to as pink sapphire. Some of them are very attractive and in demand. A problem in classification frequently arises with stones that appear red under incandescent light and light purplish-red in daylight. In order to avoid future difficulties in selling, it is recommended that such stones should not be called rubies, unless they are medium red under both light sources.

Alexandrite like Sapphire

Some sapphires show a distinct change of color from violet or purple to blue. Stones that change to a more reddish or purplish color at night from a daylight blue color are usually referred to as alexandrite like. The color change is usually weak and detracts from, rather than adds to, beauty. However, rare stones show a very strong change from an attractive daylight blue to a lovely purple-violet night color.

Colorless Sapphire

Colorless sapphires were used for many years as diamond substitutes, particularly in calibre sizes for jewelry pieces other than rings. They are usually referred to as white sapphires or rarely, as leuco sapphires. Natural colorless sapphires are seldom as transparent or as brilliant as synthetic colorless sapphires or synthetic spinels, which have replaced them for calibre use.

Light Greenish Blue

Sapphires of this color are often referred to as aquamarine sapphires or sometimes, in error, as "Oriental aquamarine".

Brown Sapphire

Transparent brown sapphires are rather rare; usually, they are opaque. If they are sufficiently silky, cabochon-cut stones may exhibit a star; if not, a term sometimes used for them is adamantine spare. Attractive transparent stones of a moderately intense brown color have been found in Cambodia.

Star Sapphire

Any sapphire that shows asterism is referred to as star sapphire. These stones are never completely transparent, because they must have enough silky, needlelike inclusions to produce a star. They occur in almost every color in which transparent sapphires exist, although orange and yellow stars are almost unknown and green is somewhat less rare. Blue ones range from a rich, deep blue , which is rare in stones with distinct stars, to those containing so little blue that they are bluish gray to almost white.

The other frequently encountered asteriated variety is the black star sapphire, so called despite the actual very dark brown, purple, blue or green color. Most black stars show strong zonal and inclusion distribution, in addition to basal twinning, which makes them subject to easy parting. As a consequence, the majority must be cut in very flat cabochons, which makes the zoning more obvious and reduces the sharpness of the star. Twinned stones frequently display a twelve-rayed star, the alternate legs of which vary in intensity and occasionally in color.

Unequal distribution of inclusions may weaken one or more, rays of a star ruby or sapphire, producing a cat's-eye effect. Also, this effect may result if the optic axis of a star stone is oriented parallel to the girdle. These are curiosities, rather than significant gem varieties, and are seldom encountered, they are, however, greatly esteemed by the gem connoisseur.

Formation of Corundum, Rubies, Sapphire

Common corundum was formed under a wide variety of geological conditions. In almost any mineral, crystals suitable for gem use occur only under unusually good conditions. Conditions conducive to ideal crystal growth seem even more rare during the formation of corundum than of most other gem minerals, for it is among the most widely occurring but least commonly transparent minerals. The right conditions seem to occur most frequently in the contact metamorphism of certain limestone's that re-crystallize into marble. In the process, the necessary impurities in the limestone, mainly aluminum oxide, are concentrated under conditions that permit them to crystallize as corundum.

Corundum also occurs in a variety of aluminum rich igneous rocks. There are some pegmatite dikes bearing a higher than ordinary percentage of aluminum in which gem quality material was formed. Also, it is occasionally found in very basic igneous rocks. It is associated in North Carolina with dunite, a basic rock composed mostly of olivine (peridot). It is also found in a very basic igneous dike in the Yogo Gulch deposit in Montana. In eastern Canada, corundum is the major constituent in syenite, a rock just slightly less acid than granite. With the exception of the Yogo Gulch mine, the gem corundum deposits of the world are almost exclusively alluvial in nature. In Burma, sapphires and rubies are found in crystalline limestone; usually, however, the concentration is too low to enable the deposits to be worked on a profitable basis.

Sources of Corundum, Rubies, Sapphire

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.

Polishing Rubies, Sapphire

Step, brilliant, mixed and calibre styles are used for transparent material, although very dark and/or semi-transparent stones are sometimes cut in cabochon. Pale stones are often cut with heavy backs to deepen the color. In order to produce the most attractive color in either transparent ruby or sapphire, the table of the stone should be oriented at right angles to the optic axis. When this is not done, rubies will appear orangey red, instead of lightly purplish red, and blue, sapphires will appear greenish blue, instead of slightly violetish blue, thus reducing their value and desirability. When orienting asteriated material, the girdle must be placed parallel to the plane in which the surface sheen is noted on the crystal (i.e. perpendicular to the optic axis); otherwise, the star will not be centered at the apex of the cabochon. Fortunately, a stone with a properly oriented star will automatically have the best color possible.

Untwined and most lightly flawed corundum is not heat sensitive to the various operations of the fashioning process, nor does cleavage pose a problem; it is, however, expensive to cut and polish. Because of its hardness, the techniques used for other materials are unsatisfactory. Cabochon material can be cut on silicon-carbide wheels, but the weels wear down at a tremendous rate. Large stones should be trimmed as closely as possible with the diamond saw. Sanding can be accomplished on a very coarse-grit cloth only. Cabochons are polished on grooved wooden wheels or pellen discs with 1200-grit diamond powder, followed by 6400 grit powder. Care must be exercised in this operation, however, since the heat generated may loosen the stone on the dop; therefore, occasional cooling is recommended.

Faceting is accomplished on diamond-impregnated cooper laps, or electroplated diamond surface laps, and polishing is done on tin or zinc laps with 14,000 to 50,000 diamond powder and oil. The finishing can sometimes be improved by following the diamond-powder polishing with tripoli. Suggested angles for the brilliant cut are 37°for the main crown facets and 42°for the main pavilion facets.

Physical & Optical Properties of Corundum, Rubies, Sapphires

Physical Properties

Chemical Composition Aluminum oxide, expressed by the formula Al2O3. The color is caused by chromium Oxide in the red, titanium and iron oxide in the blue, iron oxide in the yellow, chromium and iron oxide in the orange, iron and titanium oxide in the green, and chromium, titanium and iron oxide in the purple.
Crystallographic Character Hexagonal system. Habit: ruby usually crystallizes in six-sided prisms, terminated by flat faces (basal pinacoids) as shown in the photograph. Sapphire (except Montana) usually occurs in a double pyramid with twelve inclined faces, often modified by several extra sets of six above and below (sketch). The inclination of the pyramidal faces may be so slight that the crystals resemble simple hexagonal prisms.
Hardness 9
Toughness Excellent, except in laminated (repeatedly twinned) or fractured stones. Many star corundums contain fractures or incipient fractures that may be extended by blows delivered during ordinary wear.
Cleavage None. Parting, or false cleavage, often occurs due to twinning parallel to the base or a rhombohedral direction. Twinning is particularly common in black star sapphires, which is the reason for their usual shallow cut.
Fracture Conchoidal
Specific Gravity Ruby: 3.95 to 4.05 normally 4.00; Sapphire: 3.95 to 4.03 normally 3.99.
Streak White
Characteristic Inclusions "Silk", which is common in both ruby and sapphire, occurs in two forms: needlelike rutile crystals or long, narrow negative crystals, both of which are arranged in three sets of parallel threads that intersect one another at sixty-degree angles. Other crystal inclusions include zircon, usually surrounded by a halo of black fractures, tiny spinel octahedral, mica, hematite slabs, rounded grains of garnet, coarse rutile needles, and corundum crystals and grains of low liquid and gas filled inclusions arranged in a "fingerprint" pattern. Prominent hexagonal growth lines and color zoning are common in both varieties of corundum.

Optical Properties

Degree of Transparency Transparent to opaque.
Luster Fracture surfaces are vitreous; polished surfaces are vitreous to sub adamantine.
Refractive Index 1.762-1.770. Green sapphire may be about 0.01 higher.
Birefringence 0.008
Optic Character Uniaxial negative
Pleochroism Ruby: strong purplish red and orangey red. Blue sapphire: strong violetish blue and greenish blue. Green: strong green and yellow-green. Yellow: weak to distinct yellow and light yellow. Orange: strong yellow-brown or orange and colorless. Purple: strong violet and orange.
Dispersion 0.018
Phenomena Asterism, Very rarely a cat's-eye effect is encountered; also, an alexandrine color change from blue to purple and very rarely from green to reddish brown.
X-Ray Fluorescence Burma and Ceylon rubies: strong red. Siam ruby: weak red. Blue sapphire: usually inert, but may show a weak red glow. Green: inert. Yellow usually inert, but may show a weak orange-yellow glow. Orange: strong red. Colorless: moderate red. Violet: strong red.
Transparency to X-Rays Nearly transparent.
Ultraviolet Fluorescence Burma ruby: strong red (long wavelengths; moderate red (short wavelengths). Ceylon ruby: strong orange-red (long wave lengths; moderate orange-red (short wave lengths). Siam ruby: weak red long wavelengths): weak red to none (short wavelengths). Pink sapphire: strong orange-red (long wavelengths; very tight sapphire: strong orange-red (long wavelengths). Ceylon yellow (golden) sapphire: moderate orangey yellow (strength is in direct relations hip to depth of color in long wavelengths); weak yellow-orange (short wavelengths). Green sapphire: none. Ceylon light blue sapphire: strong orange to red (long wavelengths). Other blue stones are virtue UV inert, with the exception of some Siam stones that fluoresce greenish white under short wavelengths, thus resembling synthetic sapphires under the same conditions. Violet and alexandrite like sapphire: strong red (long wavelengths): weak light red (short wavelengths). Colorless sapphire: moderate light orange-red.
Color-Filter Reaction Ruby: strong red. Green sapphire: green. Blue sapphire: blackish, Purple and purplish-blue stones; may appear reddish.
Absorption Spectra Ruby: a strong doublet at 6942 and 6928 A.U.; which may appear as a fluorescent line; fairly distinct lines at 6680 and 6595 A.U. , broad absorption from 6200 to 5400 A.U., a strong doublet at 4765 and 4750 A.U., a weak line at 4685 A.U., and general absorption of the violet. Blue sapphire: three bands in the blue at approximately 4500, 4600 and 4700 A.U. In Australian stones all three bands are usually distinct, but only the 4500 line is usually visible in those from Ceylon. Green: same three bands but somewhat stronger. Yellow (Australian): same three bands but usually weaker. Yellow stones from other sources show no typical absorption spectrum. Purple stones may show a combination of the ruby spectrum (chromium) and sapphire spectrum (iron).

Effects Caused by:

Heat Ruby: infusible before the blowpipe or the flame of the jeweler's torch. May turn green during cooling from high temperature, but resumes red hue when completely cooled. Heating sometimes improves color by removing extraneous blue tints. Sapphire: infusible. If heated to a sufficiently high temperature, it usually loses color permanently. Laminated stones may split.
Acids Attacked with difficulty. May lose polish if boiled in a diamond-cleaning kit.
Irradiation Some experiments with the bombardment of light-yellow sapphires by subatomic particles have shown that a desirable yellow to brownish-yellow color can be produced. X-rays quickly change pale yellow sapphires to a rich yellow that fades on exposure to strong light.

Test and Identification of Corundum

Because corundum is such an important gem species and the major problem in testing is to distinguish the natural from the synthetic, detailed suggestions for making this separation are reserved for Assignment #34.

In this later assignment, the student will become familiar with the various synthesizing processes, a knowledge of which is essential to an understanding of the characteristics of synthetics. Therefore, the information presented here is confined to suggestions for separating natural corundum from its most-often encountered imitators, both natural and manufactured, with the exception of its synthetic counterparts.

Despite the fact that garnet is singly refractive and ruby doubly refractive and the colors are rarely the same, those with little experience in gem testing seem to have more difficulty in separating these two stones than any others of natural origin. The reason for this is that garnet frequently shows strong anomalous double refraction and may therefore appear doubly refractive in the polariscope. When a dark-red stone with a refractive index of approximately 1.77 becomes alternately tight and dark in the polariscope's dark position, it should be checked further with the dichroscope. (An alternate means of checking for dichroism is to rotate the stone between the Polaroid plates in the polariscope light position.) A ruby will show strong pleochroism, which can be observed in the dichroscope or in the polariscope's light position. This may be checked further by rotating a Polaroid plate before the eyepiece of a refractometer: if the stone is doubly refractive, in the direction of maximum birefringence the two readings will be evident as a slight movement of the shadow line that indicates the R.I. as the plate is turned. Also, if the tester has developed an ability to distinguish doubling of back-facet junctions, even in stones of fairly low birefringence, he should be able to detect the moderate doubling in a faceleted ruby. Further, using long wavelength ultraviolet light in a darkened room will show fluorescence in ruby, but never in garnet. Finally, the absorption spectrum of ruby is entirety different from that of garnet when the stone is viewed through the spectroscope.

Since a garnet and glass doublet may have a color that is virtually indistinguishable from that of ruby and an R.I. on the table within the range of corundum, it is also frequently mistaken for ruby. Immersion in a high-index liquid is not as helpful in detecting an all-red doublet as