Origin of name
Two large rubies belonging to the Burmese royal family weighing 37 carats and 47 carats were brought into England in 1875 for sale in the British market. J. N. Forster decided to re-cut the two stones as they did not conform to British standards. The smaller stone was re-cut to 32.31 carats and the larger stone to 39.56 carats, and subsequently put up for sale. The two re-cut rubies then came to be known as the “J. N. Forster Rubies.”
Characteristics of the gemstones
The two rubies must have been the finest pigeon’s blood color rubies ?
The smaller stone which weighed 37 carats was said to be a cushion-cut rich-red stone. The larger stone was a drop-shaped stone of 47 carats, probably of the same rich-red tone. The two rubies belonged to King Mindon Min (1853-78) whose kingdom was based in Mandalay in central Burma. Thus the rubies undoubtedly originated in Mogok, Burma, renowned for its high quality rubies. According to Streeter, gem experts of the time had pronounced the rubies to be of exceptional quality, unrivaled for rubies of such large size. This is further confirmed by the fact, that extra security precautions were taken, by providing a military escort to the persons who carried the two stones to the London-bound ship. Thus going by all these evidences, and the fact that the stones were a rich-red color, we can conclude that the two rubies must have belonged to the ko-twe variety of rubies in the Burmese system of classification, which is the highest quality of rubies having the finest hue known as pigeon’s blood color. The clarity of the stones must also have been quite good, at least “eye clean,” given that inclusions in rubies are generally the rule rather than the exception.
The rubies are re-cut in London by J. N. Forster
The rubies were re-cut in London to conform to European standards and after re-cutting the smaller ruby weighed 32.31 carats and the larger ruby 39.56 carats. In all probability the original cushion and drop shapes of the two stones must have been maintained during the re-cutting.
The significance of fluorescence in Burma rubies
Burmese rubies are noted for their strong red fluorescence in ultra-violet light and in sunlight rich in u-v light. This property of Burmese rubies impart a warm red glow to the gemstones, which otherwise would be dull red, like the Thai and Cambodian rubies, which show only a weak fluorescence. The dispersion of rubies is only 0.018 as compared to diamonds which have a dispersion of 0.044. The high dispersion of diamonds impart “fire” to the stones, which is so characteristic of diamonds. The low dispersion of rubies on the other hand should result in a lack of “fire” in these stones, making them dull in appearance. However, the tendency of Burmese rubies to show a strong red fluorescence, more than compensates for the lack of fire due to low dispersion.
The glowing red color of Burmese rubies which has been compared to a red traffic light or stop light by Richard Hughes is therefore a combination of intense-red body color and strong-red fluorescent emission. The red fluorescence tends to cover the dark areas in the stone that are caused by “extinction”, a phenomenon caused when light escapes through a deep or shallow facet from the pavilion of the stone, instead of being totally and internally reflected.
Another significance of fluorescence in Burma rubies is that the combination of the intense-red body color and strong-red fluorescence might possibly indicate the country of origin of the gemstone. However, countries like Afghanistan and Kenya also produce rubies with the same combination of color and fluorescence, even though they are quite rare. Recently, Vietnam has also been producing Burma quality rubies, with the same combination of properties.
Other characteristic properties of Rubies
Ruby is the red variety of the mineral called corundum (crystalline aluminum oxide) in which the red color is caused by some atoms of aluminum in the crystal lattice being displaced by chromium. All other varieties of the mineral corundum such as violet, blue, green, yellow, orange and white are called sapphires.
Rubies crystallize in the trigonal (hexagonal) system and form short hexagonal prisms. The hardness of ruby is 9 on the Mohs scale. The excellent hardness and toughness of ruby make them ideal for setting in durable jewelry either alone or in combination with diamonds. The specific gravity of ruby, varies from 3.99 to 4.02. They have a double refractive index, 1.761 and 1.769, and birefringence which is the difference between the two is 0.008. The dispersion of rubies is 0.018, which is low compared to diamonds, which is 0.044.
Rubies are strongly dichroic, with the deepest color perpendicular to the c-axis. The two colors that appear in the dichroscope are intense purple-red and light orange-red. Dichroism can be used to distinguish between rubies and other look-alikes such as red spinels and red garnets, which do not show this property, being crystals of the cubic system, and are singly refractive.
The fluorescence shown by rubies vary with the country of origin. The Burmese rubies show a strong red fluorescence in u-v light or in strong sunlight, due to the presence of only chromium as the coloring agent. The Thai and Cambodian rubies show a weaker fluorescence due to the presence of iron (Fe) together with chromium (Cr) in the crystal structure. The Sri Lankan rubies show a strong orange-red fluorescence in long wave length u-v light (4000A?-3000A?) and a less strong fluorescence in short wave length u-v light (3000A?-2000A?), attributed only to the presence of chromium.
All natural rubies have mineral or fluid inclusions. Common inclusions found in Burma rubies are rutile, calcite, apatite, olivine, sphene and spinel. In Thai rubies the common inclusion found is iron sulphide known as pyrrhotite. In Sri Lankan rubies the inclusions found are rutile, zircon, and radiation haloes.
History of the J. N. Forster Rubies
King Mindon Min’s period of rule
The rough Forster rubies after their discovery in Mogok during the reign of King Mindon Min (1853-78), entered the treasury of the king, in conformity with the stringent decree issued by the king that all rubies beyond a certain value and size should be surrendered to the king’s treasury. Any breach of the rule was dealt with severely ending up in capital punishment. But, Mindon Min has gone down in the history of Burma, as one of the most cruel kings, the country had ever seen, for the decimation of an entire village by burning its people alive, for the fault of one of the villagers who surrendered only the larger half of an enormous rough ruby to the king, the lesser half being smuggled across to India, to be sold in Calcutta at a profit. The villagers were so terrorized that most of its inhabitants fled en masse from the ruby mining areas, and when the British captured upper Burma in 1885, the mining region in Mogok was totally deserted.
In spite of the harshness of his rule Mindon Min’s period of rule is considered as a golden age of Myanmar culture and religious life. After losing southern Burma to the British in 1852, following the second Anglo-Burmese war, Mindon Min built a new capital in Mandalay. The palaces and monasteries built by him during this period have earned a distinction as masterpieces of traditional Burmese architecture. He also converted Mandalay to a center of Buddhist learning, and convened the Fifth Buddhist Council in 1871 in an effort to revise and purify the Buddhist Pali scriptures.
Mindon Min decides to dispose of the Forster rubies
The Foster rubies were cut and polished in Mandalay by Burmese cutters and polishers, that resulted in the 37-carat cushion-cut ruby and the 47-carat drop-shaped ruby. In the year 1875, just three years before his death, Mindon Min had to face severe financial constraints and was advised by his ministers to sell some of his valuable rubies, in order to overcome his financial problems. In keeping with this advice he decided to send two of his most exceptional rubies to the London market for sale. The rubies selected were the Forster rubies, which were dispatched to London by steamer under tight security. According to the London jeweler and writer Edwin Streeter, the two Foster rubies that were brought into England in 1875, were the two most important rubies ever known in Europe at that time.
Before the rubies were put out on sale James N. Forster of London, got the stones slightly re-cut, possibly to eliminate some flaws or inclusions and improve the appearance of the stone in keeping with western standards of cutting, and the smaller stone was cut into a cushion-shape of 32.31 carats, and the larger stone to a drop-shape of 39.56 carats. The two rubies came to be known as the Forster rubies. The smaller stone was eventually sold for £ 10,000 and the larger stone for £ 20,000. The prices fetched were indeed record-breaking considering the period of the sale.
The present whereabouts of the J. N. Forster rubies are unknown. Mindon Min died in 1878 and was succeeded by his younger son Theebaw, who ruled until 1885, the year upper Burma was annexed by the British.
1) Ruby & Sapphire – Richard Hughes
2) Ruby & Sapphire Notes – University of Texas, Austin.
3) The Encyclopaedia Britannica – 2006