Guide to Sapphire
History, Lore and Appreciation
If blue is the color you think of when the word “sapphire” is said, you are very close to its root. It derives from Hebrew and Arabic terms safir, meaning blue, and sapphiros, meaning blue in Greek. In ancient times, such words referred to a blue gem material that was likely lapis lazuli. Conversely, the ancients called the today’s sapphire “hyacinth,” due to its color similarity to blue hyacinths. Obviously, that term has changed with the passage of time, though a lovely poem about gems by Marbode, Bishop of Rennes, written approximately 1000 years ago speaks of the colors of hyacinth, as follows:
Three various kinds the skilled as Hyacinths name,
Varying in color, and unlike in fame: One, like pomegranate flowers a fiery blaze
And one, the yellow citron’s hue displays One charms with paley blue the gazer’s eye,
Like the mild tint that decks the northern sky,
A strengthening power the several kinds convey,
And grief and vain suspicions drive away. The blue sort feels heaven’s changes as they play,
Bright on the sunny, dull when dark the day,
But best that gem which not too deep a hue, O’erloads, nor yet degrades too light a blue.
Even then, a classification of hyacinth’s beauty was tacitly underway. The reference to blue hyacinths, lovely flowers, remains an apt association, but the term began to fade. In the 15th Century, the naturalist Camillo Leonardo spoke and wrote about “sapphirini.”
Modern day usage of sapphire includes almost all colors of the spectrum
other than just blue – as Marbode’s poem suggests. Sapphire, in fact, can be any color but red. That’s because red corundum (though essentially the same mineral as sapphire) is classified as a ruby. In short, the difference between ruby and sapphire is that only ruby can be red. So in separate colors of sapphire, descriptions are preceded by a color designation, such as “yellow sapphire.” Corundum, other than red or blue, may also be referred to as “fancy sapphire.” Fine quality blue sapphire has interesting color descriptors that are often comparisons to a flower, as in ancient times. This includes the often-used “cornflower blue.” Others may compare sapphire colors to other natural vibrant colors, such as a peacock’s feathers.
The allusion to flowers does not end there. Color variations are what make this variety of corundum so interesting, as are the “mixed colors.” One important gem with a blend of colors, which captivates the imagination, is the padparadscha sapphire. The trade term, Padparadscha (which derives through the German language from the Sinhalese word padmaraga, meaning lotus color) denotes an extraordinary and rare variety. The term is only applicable to sapphires with medium pinkish orange to orange-pink colors.
In recent years, there has been a growing appreciation for phenomenal gems – of which sapphire enjoys two principal varieties: Star sapphire in blue and various other colors with a six-rayed star, (and rarely a twelve-rayed star) cut as cabochons, as well as color-change sapphires have both received increasing attention in recent years.
Birthstones and Anniversaries
Sapphire is the birthstone for the month of September. It is used to celebrate 5th and 45th anniversaries.
Description and Properties
A variety of the mineral species corundum, forming in the trigonal crystal system with the chemical composition of Al2O3
Colors: Blue sapphire: very light to very dark violetish blue to greenish blue.
Fancy Colors: All colors of the corundum species excepting blue and red (blue sapphire and ruby respectively). These colors include green, yellow, orange, pink, purple, violet, brown, black, and colorless. Sapphire may also contain two colors, mixed colors or other variations. In recent years, pale colored sapphire has come to be known as “pastel sapphire” in the trade.
Refractive Index: 1.762 to 1.770 (+0.009, -0.005)
Birefringence: 0.008 to 0.010
Specific Gravity: 4.00 (+0.10, -0.05) Cause(s) of color: Blue: iron and titanium. Green: iron or iron and titanium. Yellow: iron and color centers; orange: iron (and possibly chromium in padparadscha variety). Purple: varying traces of iron, titanium and chromium. Pink: chromium; possibly titanium. Color change: combined presence of chromium, vanadium, iron and titanium.
Mohs Hardness: 9
Internal identifying characteristics: Inclusions in sapphire may be composed of fine rutile needles (called silk), which may intersect at 60-degree angles. In such cases, when the gem is cut as a cabochon, a star effect may occur. Included zircon crystals or crystals of different minerals, fluid inclusions, fingerprints or partially healed fractures, and negative crystals with liquid-gas (CO2) may also occur and color zoning, particularly seen in angular patterns.
Heating: This treatment is undertaken to increase transparency by reducing the opacity of clouds of rutile inclusions. It has also been performed on low quality sapphire material from Sri Lanka, known as geuda, since the 1970s. This is a high temperature treatment that results in strong blue and yellow colors. Heating may also cause some overly dark blue or green sapphire to be lightened in tone, or to turn purplish sapphire into pink colors. Heating at high temperature in a moderate pressure environment has been recently reported to generate treated blue sapphire.
Diffusion: Heating some sapphire at very high temperatures with chemical additives causes lattice diffusion of those additives. Elements, such as beryllium or titanium, are diffused into the corundum crystal lattice, causing colors in the gem being treated to deepen or change.
Coating: On rare occasions, some sapphire is coated with a thin film to deepen or change its color appearance.
Irradiation: Some colorless to near colorless sapphire can be turned orange or yellow though irradiation. Color in irradiated sapphire fades over time.
Glass filling in cavities and fissures: While this treatment is less prevalent in sapphire than it is in ruby, it should be noted that any gem material with surface reaching fissures might be subjected to infilling of glass or other substances, with the goal of increasing the transparency of the gem.
Several factors may be used to judge fineness in sapphire, though ultimately, the beauty of a gemstone remains in the eye of the beholder. Fine quality blue sapphire should possess the ability to be spotted from across the room because
of its depth of color and saturation. The transparency of sapphire also comes into play. Because inclusions can cause some gems to have milky coloration, this becomes a detriment if it also causes a perceived loss of blue. In one notable exception, haziness is not only expected – it is desired, and that is in the finest sapphire from Kashmir. The haziness (often referred to as sleepiness) acts
to diffuse light and color, resulting in magnificently even blue coloration.
The specific color of blue sapphires, often described in the trade with descriptors such as “Royal Blue,” “Cornflower Blue” or “Peacock Blue,” also affects their desirability. Geographical provenance has been regarded as a value factor (e.g. Kashmir, Burma, Sri Lanka) in spite of the scientific recognition that it is more reliable to determine geological origin than geographical origin. This is because there are well-documented situations of overlapping gemological data.
In recent years, gemstones coming from various localities around the world, such as Madagascar, or the Umba River Valley in East Africa, have supplied a unique palette of colors that are desirable for collections, especially in suites showing an array of hues. East Africa and Madagascar have joined other sources such as Sri Lanka, in bringing to market rare color change sapphire, many changing from a blue grey color in daylight, to a violet or purple color in incandescent light. Star sapphire with strong color in which the “legs” of the star are girdle-to-girdle, straight and unwavering is desirable. Fine padparadscha is also considered collectible.
Sri Lanka and Myanmar (Burma) are historic sources for sapphire and produce some of the world’s finest gems. In extremely high qualities, Kashmir has emerged as the preeminent source for blue sapphire, especially in the late 19th century. Sri Lanka is the classic source for padparadscha sapphire, though other sources also now produce mixes of pink and orange colors as well. Australia, Thailand, Cambodia, Kenya, India, Tanzania, Madagascar, Malawi, Greenland, Vietnam, Nigeria, Ethiopia, China, and the United States all produce blue sapphire, as well as many fancy colored hues.
Cutting, Care and Cleaning
Sapphire is mostly cut in traditional pear, round, oval, cushion and emerald cut outlines. Sapphire is extremely durable due to its hardness and exceptional toughness, second after diamond on the Mohs hardness scale. Sapphire jewelry may be cleaned in an ultrasonic cleaner, or it may be steamed. But this should follow close inspection to determine if there is any surface- reaching fissure that could expand, possibly causing damage. As with most gemstones, a soft moistened cloth, or a soft bristle toothbrush may be used to clean the gem.
Source: CIBJO Retailer Reference Guide, cibjo.org.