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Star Sapphire (Asterism)Certain varieties of sapphire can exhibit a six-pointed "star" or "asteriated" effect (above, right) from light reflections bouncing off of microscopic needle-shaped rutile crystals (also referred to in the ruby trade as "silk") which intersect at 60¡ angles. Star sapphires are semi-transparent to opaque, and the star effect is more apparent when a cabochon cut is used for the stone. Sapphire (Corundum) Chemistry & Physical Properties
Sapphire (Corundum) Optical Properties
Color Grading of Blue SapphireSapphire gemstone color-grading is broken into three quantifiable categories: intensity (saturation), hue (color), and tone (lightness/darkness). The GIA specifies thirty-one individual gemstone hues. Relating to sapphire, terms such as "blue," "slightly greenish blue," "very slightly greenish blue" are used to describe color tendencies. The color-grading nomenclature also specifies six levels of saturation ranging from "grayish" (neutral grey) to "moderately strong" to "vivid," and nine levels of tone ranging from "very very light" to "very very dark." A numerical value is assigned to each label for use in a gemstone color grading report.  The most desirable blue sapphire color is an intense, pure, and primary blue with a slight hint of violet and very little of the gray or green color components. For a blue sapphire to receive a perfect '10' quality rating it would have a "violetish/blue" hue, with a 6 or "medium dark" tone, and 6 or "vivid" color saturation level. Specific color grades of blue sapphire are commonly refers to as: Ceylon Blue, Cornflower Blue, Electric Blue, Kashmir Blue, Royal Blue, Sky Blue, Velvet Blue, and Violet Blue. High-quality Kashmir, velvet-blue and Cornflower-blue sapphires will maintain their color and intensity under a variety of lighting conditions from bright sunlight to dim artificial light. Color Zoning in SapphireMost sapphire will exhibit moderate to strong color-zoning, caused by growth layers as the crystal is formed, however, sapphire from Burma may have very uniform color with little or no color zoning. Sapphire color-zoning may appear as concentric hexagonal rings (below, left), that run parallel to the prismatic outer facets of the rough crystal.
Skilled gem-cutters will insure that the faceted stone has some color in the culet to enhance the color when viewed through the table and crown. From the side however, these stones will have little color. Sapphire MiningThe world's oldest sapphire mines are situated in Ceylon (Sri Lanka), and Kashmir (India and Pakistan). Sapphire deposits typically occur within metamorphic rock and pegmatite occurrences, or in gem-bearing, or "gemmiferous" gravels that are found along river-beds and ancient alluvial secondary deposits. These river gravels may also contain ruby, spinel, quartz, and zircon. Mining is typically a non-mechanized small scale operation involving several workers who dig a small pit around four feet deep, excavating the gravels with woven baskets. The material is then washed (sifted) using a circular woven sieve made of thin strips of bamboo. Kashmir SapphireHistorically, the finest sapphire in the world had originated from India's northwestern region of Kashmir, along the Pakistani/Indian boarder in the western Himalayas. The Kashmir region was famous for its blue sapphires which exhibited an intense, vivid blue hue that came to be known as "Kashmir blue" (photos, below).
The Kashmir region's sapphire deposits were mined extensively during a brief decade-long period in the late 1800's, after a earthquake-induced landslide unearthed a large deposit, but the region was fully depleted by the early 1900's, and Kashmir is no longer a significant source for sapphire. This fact adds significant value to any stone that is positively identified as a true Kashmir sapphire. Thai & Burmese Mogok SapphireSecond only to Kashmir in quality and mystique, some of the world's most valuable sapphire, ruby and spinel has been found within the Mogok Stone Tract situated along the high-altitude Mogok Valley, about 175 km northeast of Mandalay, in Myanmar (Burma). The name "Mogok" is derived from the Burmese term "bamar moegokesetwaing" or "horizon." Within the 4,800 square-kilometer area that comprises the Mogok Valley, there are over 1,000 ruby and sapphire mines. In 1972 the world's largest sapphire, at 63,000 carats, was found in Mogkok.
Burmese sapphire mining operations are conducted by state-owned mining enterprises such as Myanmar Gems Enterprise (MGE) and Myanmar Economic Holdings (MEH). During the early 1990s, the Thai border town of Mae Sai was the main transit-point for illegally smuggled Mogkok sapphires and rubies, but by 1995 the Myanmar government had slowed down smuggling operations, and Burmese sapphire is now in scarce supply.
Myanmar's former capital city of Yangon (Rangoon) is now the officially sanctioned gem-trading capital within Myanmar. Notable ruby and sapphire mines within Burma are MGE's Yadana Kadeikada, Linyaung Chi, and Shwe Pyi Aye gem mines, all near Kyaukpyattha Village in central Mogok. Sapphire mining within Thailand occurs primarily within the Chanthaburi and Trat provinces, located in the southeastern part of the country bordering Cambodia, and near the northern boarder with Myanmar in the province of Kanchanaburi. Chanthaburi is known for its prized yellow sapphire called "Mekong Whisky," which has a golden brownish-yellow to orange hue. Sapphire Mining in Sri LankaSapphire from Sri Lanka (Ceylon) has supplemented the declining supply emanating from Myanmar and Thailand in recent decades. Sri Lanka is known for producing the highest quantity of larger, 100+ carat stones in the world. Yellow sapphire from Sri Lanka is called "pushparaga" in Singhalese ("pukhraj" in Hindi), and can be comparable in value to the finest Mogok sapphire. Pushparaga, also known as "Oriental topaz" or "hyacinth" has a golden or honey yellow color with brownish secondary hues that resembles actual topaz (pushkaraj).
There is also a very rare orange-pink or red-orange Sri Lankan variety called "padparadscha sapphire" which can be as valuable as diamond. The principle mining area of Sri Lanka is situated around Ratnapura ("City of Gems") 60 miles southeast of Colombo. Ceylon yellow sapphires display a pure canary-yellow, brownish-yellow compared to other varieties of yellow sapphire which can have greenish overtones. Australian SapphireThe Central Highlands and Gemfields regions of Queensland, Australia have also produced some of the finer specimens of greenish-yellow, golden, green, orange, and blue sapphire, as well as the unusual "parti-colored," or multi-colored sapphires which are marbled with hues of blue, green and yellow.
Australia's largest sapphire mines are the underground Bedford Hill, Normans Hill and Scrub Lead mines, located in Rubyvale township, Gemfields. In Australia, freelance prospecting, called "fossicking," is a popular vocation, and each year in early August, Fossickers from around Queensland attend the Festival of Gems "Gemfest" which celebrates the region's mining heritage. Sapphire Mining in Madagascar & TanzaniaWith the decline in production of Burmese and Thai sapphire, southeastern Africa and the island of Madagascar have become major new sources for sapphire within the last 40 years. Madagascar sapphire is found in the Andranondambo and Ilakaka mining regions in the southern part of the island.
A unique reddish-pink to mandarin-orange sapphire was discovered in Tanzania's Umba Valley during the 1960s. This variety was found in the Gerevi Hills and Lelatema Mountains north of the Umba River, in the Arusha Region of Tanzania. The Tundouro mine in Tanzania also produces a yellow sapphire with a distinctive greenish-yellow color. On To: Sapphire Enhancements & Synthetic Sapphire Burmese Mong Hsu & Mogok Sapphire 
Ted Themelis, Mogok: Valley of Rubies & Sapphires Richard W. Hughes, Ruby and Sapphire Emporia State, Ruby and Sapphire - Varieties of Corundum Judith Osmer, Ruby and Sapphire Pala Gems, Kashmir Sapphire Mines G Du Toit, R Hughes, J Koivula. Beryllium-Treated Blue Sapphires Judith Crowe, The Jeweler's Directory of Gemstones Cally Hall, Gemstones Walter Schumann, Gemstones of the World Renee Newman, Gemstone Buying Guide Antoinette L . Matlins, Antonio C. Bonanno, Gem Identification Made Easy Paul R. Shaffer, Herbert S. Zim, Raymond Perlman, Rocks, Gems and Minerals R. V. Dietrich, Brian J. Skinner, Gems, Granites, and Gravels James E. Tennent, Ceylon Sapphire & Gems Simply Sapphires. Certified Large Sapphires Fossicking.com. Sapphire Fossicking in Queensland, Australia United Nations. Atlas of Mineral Resources of the ESCAP Region | Copyright © 2012 AllAboutGemstones.com. All rights reserved. | | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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: Sapphire Corundum
