Star Ruby shows asterism, a six-rayed star that shimmers over the surface of the stone when it is moved. Ruby is red corundum, all other color varieties of corundum being referred to as sapphire. Corundum is the second hardest substance on the Mohs scale, with a rating of nine. Diamond tops that scale with a ten. That hardness combined with the rich color and silky shine make fine rubies so valuable and secure them a place in the group of four so-called "precious" stones, along with diamond, emerald and sapphire. Ruby is named after the Latin word "ruber" for red. Star rubies contain unusual tiny needle-like inclusions of rutile. Aligned needles that intersect each other at varying angles produce a phenomenon called asterism The six-rayed-star light effect appears most clearly under natural light. Included rutile needles cause the star effect. Rubies range in color from pinkish to orangey and purplish and brownish red, depending on the chromium and iron content of the stone. The most desirable color is the so-called "pigeon’s blood," a pure red with a hint of blue, only found in the mines of Myanmar. Ruby is one of the most expensive gems, large rubies being rarer than comparable diamonds. Ruby is the birthstone for those who are born in July. Ruby is also used to celebrate a couple's 15th and 40th anniversaries.
Rubies range in color from pinkish to orangey and purplish and brownish red, depending on the chromium and iron content of the stone. The most desirable color is the so-called "pigeon’s blood," a pure red with a hint of blue. The distribution of color is often uneven, in strips or spots. Large star rubies are rare. The most desirable color is the so-called "pigeon’s blood," a pure red with a hint of blue. Color saturation is extremely important as well. Star Ruby shows pleochroism, which means that the color varies with the direction of viewing. The six-rayed-star light effect shimmers best over the surface of the stone when moved in daylight. Many rubies will fluoresce in long or short wave UV and this property can often be used to help identify a stone's geographic origin. Burmese rubies often fluoresce so strongly that the effect is noticeable even in sunlight, such stones seem literally to glow, and are greatly admired. Thai stones generally lack this property. Transparent rubies are favored, but a Star ruby actually requires inclusions. Only oriented rutile crystal inclusions cause the six-rayed-star light effect (called asterism) that convert a ruby into the desired Star ruby. Star rubies are cut en cabochon.
For centuries the most important deposits are in upper Myanmar (Burma) near Mogok. Only one percent of the production is of gem quality. Some of the rubies are of pigeon’s blood color and considered to be the most valuable rubies of all. In the early 1990's large new deposits were discovered at Mong Hsu. Rubies found in Thailand (Chanthaburi district) often have a brown or violet tint. The Thai ruby production unfortunately is declining. The deposits are located in the southwest of the island in the Ratnapura district. Rubies from those deposits are usually light red to raspberry red. On the upper Umba River in northwest Tanzania are deposits for gemstone quality rubies that are violet to brown-red. A few opaque rubies are mined as well. Other deposits of importance are found in: Afghanistan, Cambodia, Kenya, Madagascar and Vietnam. Less important deposits are found in Australia, Brazil, India, Malawi, Nepal, Pakistan, United States and Zimbabwe.
The most common treatment for ruby is heat treatment. Stones, generally before they are cut, are heated to between 1700 to 1800 degrees Celsius (3100-3300 degrees F) for several hours. Heating often improves color and clarity.
Famous stones of outstanding beauty and color are the "Rosser Reeves Star Ruby," of 138.7 ct, to be seen at the Smithsonian Institution in Washington and the "De Long Star Ruby," weighing 100 ct, in the American Museum of Natural History in New York.
Color: Varying red
Chemical composition: Al2O3 aluminum oxide
Crystal system: (Trigonal) hexagonal prisms or tables, rhombohedrons
Hardness: 9 (Mohs scale)
Specific gravity: 3.97 - 4.05
Refractive index: 1.762 - 1.778
Absorption spectrum: 694, 693, 668, 659, 610-500, 476, 475, 468
Fluorescence: Strong carmine red.
For a long time India was considered the classical source for rubies. In the Sanskrit language ruby is called "ratnaraj," which translates as "King of Gemstones." In ancient times one of the chief attractions of ruby has been its protection from misfortune and bad health. Ruby is the birthstone for those who are born in July. In the Zodiac scheme, ruby is sometimes is associated with Capricorn. Ruby is also used to celebrate a couple's 15th and 40th anniversaries.
In Antiquity, as well as in the Middle Ages, people believed that the cosmos is reflected in gemstones. Ruby is assigned to the planets Mars and Pluto.
The healing powers of gems remain a controversial issue, but are mentioned for centuries by healers, shamans and medicine men. Whether it's a fact or a placebo effect doesn't matter if it helps. The safest approach is to wear the gemstone in skin contact to the troubled part of the body. Ruby is said to be a general health protector and, in particular, to be good for backache and toenail problems.
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