Sapphire Buying Guide
The term sapphire alone describes the blue variety of gem corundum. Other colors have a color prefix, i.e., yellow sapphire, green sapphire, etc. The term ruby is reserved for corundums of a red color. In Asia, pink corundums are also considered rubies. Outside of Asia, such gems are generally termed pink sapphires.
For sapphire, the intensity of the blue color is the primary factor in determining value. The ideal stone displays an intense, rich blue without being dark or inky. Stones which are too dark and inky, or too light in color, are less highly valued.
Sapphires generally look best viewed with fluorescent light or daylight (particularly around just after sunrise and before sunset). Incandescent lights, whose output is tilted towards the red end of the spectrum, do not do most blue sapphires justice.
In terms of clarity, sapphires tend to be cleaner than ruby. Buyers should look for stones which are eye-clean, i.e., with no inclusions visible to the unaided eye. In the case of some sapphires, extremely fine silk throughout the stone can actually enhance the value. This is the case with the famous sapphires from Kashmir, which display a velvety blue color with little extinction across the face.
While a certain amount of silk is necessary to create the star effect in star sapphire, too much silk desaturates the color, making it appear grayish. This is not desirable.
In the market, sapphires are found in a variety of shapes and cutting styles. Ovals and cushions are the most common, but rounds are also seen, as are other shapes, such as the heart or emerald cut. Slight premiums are paid for round stones. Cabochon-cut sapphires are also common. This cut is used for star stones, or those not clean enough to facet. The best cabochons are reasonably transparent, with nice smooth domes of good symmetry.
Sapphire is one of the world’s most expensive gems, with prices similar to those fetched by fine ruby or emerald. But like all gem materials, low-quality (i.e., non-gem quality) pieces may be available for a few dollars per carat. Such stones are generally not clean enough to facet. The highest price ever paid for a blue sapphire was the 22.66-ct. unnamed Kashmir sapphire once owned by James J. Hill (the “Empire Builder”), which sold in 2007 for $135,216/ct. This sale barely topped the previous record: the 62.02-ct. Rockefeller sapphire, which sold in 2001 for $48,871/ct.
Blue sapphires occur in far larger sizes than ruby, with Sri Lanka being the home of most of the faceted sapphires of quality in the 100-ct. plus range. Any untreated ruby of quality above two carats is a rare stone. Fine untreated rubies above five carats can be considered world-class pieces.
Sapphire may display asterism, the star effect. Fine star sapphires display sharp six-rayed stars well-centered in the middle of the cabochon. All legs of the star should be intact and smooth. Just having a good star does not make a stone valuable. The best pieces have sharp stars against an intense blue body color. Lesser stones may have sharp stars, but the body color is too light or grayish. On occasion, 12-rayed star sapphires are found.
The name “sapphire” is believed to be derived from the Greek sappheiros, a word for blue. It is likely that the word sapphire was first applied to laps lazuli from Afghanistan. According to Oriental beliefs, sapphire is the gem of Saturn. It is also the birthstone for September.
The original locality for sapphire was most likely Sri Lanka (Ceylon). Fine stones have also been found in Kashmir (India), Mogok (Burma), Madagascar, Thailand and Cambodia. Dark, inky blue sapphires come from Australia, China, Vietnam, Laos, Nigeria and a host of other localities. Fine blues of small size have been mined at Yogo Gulch, Montana (USA), while lesser stones have been produced elsewhere in Montana. Other sapphire localities include Kenya, Tanzania, Malawi and Rwanda.
Today, the vast majority of blue sapphires are heat-treated to improve their appearance. The resulting stones are completely stable in color. In lower qualities, heat treated stones sell for roughly the same as untreated stones of the same quality. However, for finer qualities, untreated stones fetch a premium that is sometimes 50% or more when compared with treated stones of similar quality. Other treatments, such as oiling, dying and surface diffusion are seen on occasion. As with all precious stones, it is a good practice to have any major purchases tested by a reputable gem lab, such as the GIA or AGTA, to determine if a gem is enhanced.
Synthetic blue sapphires have been produced by the Verneuil process since about 1908 and cost just pennies per carat. Blue sapphire has also been produced by the flux, hydrothermal, floating zone and Czochralski processes, but such stones are rarely encountered. Doublets consisting of natural sapphire crowns and synthetic sapphire pavilions are fairly common, particularly in mining areas. Synthetics are also common at the mines, in both rough and cut forms.
According to Indian astrological beliefs, sapphire is associated with the planet Saturn. Although the blue sapphire traditionally comes from Sri Lanka and Burma, it is rarely used in traditional Indian jewelry and Indian jewelers are sometimes reluctant to handle the stone associated with this powerful planet. Although no superstitions of this kind are associated with Islam, the gem was not commonly used even in the Mughal courts. No such fear exists in the West, an sapphire is one of the most popular of all gems. In the modern Western system, sapphire is the birthstone of September.
Properties of Blue Sapphire
|Sapphire (a variety of corundum)|
|Refractive Index||1.762–1.770 (0.008) Uniaxial negative|
|Crystal System||Hexagonal (trigonal)|
All except red (ruby)
|Pleochroism||Strongly dichroic: violetish blue/greenish blue|
|Phenomena||6 or 12-rayed star|
|Handling||No special care needed|
|Enhancements||Frequently heated; occasionally oiling, dying, surface diffusion|
For further information on sapphire, see also:
- Kashmir Sapphires – The first eyewitness account of the fabled Kashmir sapphire mines in northern India, 1889, by T.D. LaTouche. Complete with period and modern photos.
- Ruby & Sapphire Deposits of Moung Klung, Siam – 1894 account of mining ruby and sapphire in Thailand. By Henry Louis.
- Ruby & Sapphire by Richard W. Hughes, the finest book ever written on the subject.