Sapphire is the birthstone for September and the gem of the 5th and 45th anniversaries.
Blue sapphire belongs to the mineral species corundum. It can be a pure blue but ranges from greenish blue to violet-blue. The name “sapphire” can also apply to any corundum that’s not red and doesn’t qualify as ruby. These include fancy sapphires and can come in violet, green, yellow, orange, pink, purple, and intermediate hues. Some sapphires display the phenomenon known as color change, most often going from blue in daylight or fluorescent lighting to purple under incandescent light. Sapphires can even be gray, black, or brown.
Fancy sapphires are generally less available than blue ones, with some colors being scarce, especially in extreme sizes. Yet fancy sapphires create a rainbow of options for people who like the romance associated with this gem, but who also want something unique.
The mineral corundum is composed only of aluminum and oxygen, and it requires a growth environment that’s free of silicon. However, silicon is a very common element, making natural corundum somewhat rare. In its purest state, corundum is actually colorless. Colorless sapphires were once popular diamond imitations, and they’ve staged a comeback as accent stones in recent years. Most corundum contains color-causing trace elements. When the trace elements are iron and titanium, the corundum is blue sapphire.
Corundum can show a phenomenon called asterism, or the star effect. This phenomenon usually appears as a six-ray star pattern across a cabochon-cut stone’s curved surface. The star effect can be seen in ruby or any color of sapphire, and it arises from white light reflecting from numerous tiny, oriented needle-like inclusions.
Besides fancy sapphire and star corundum, there’s another interesting variety: color-change sapphire. These fascinating stones change color under different lighting. Their presence adds a special dimension to the already amazing corundum family of gems.
Both blue and fancy sapphires come from a variety of exotic sources including Madagascar, Tanzania, Sri Lanka, Myanmar, and Australia.
In folklore, history, art, and consumer awareness, sapphire has always been associated with the color blue. Most jewelry customers think all sapphires are blue, and when gem and jewelry professionals use the word “sapphire” alone, they normally mean “blue sapphire.”
FACTS
MINERAL: Corundum
CHEMISTRY: Al2O3
COLOR: Every color but red
REFRACTIVE INDEX: 1.762 to 1.770
BIREFRINGENCE: 0.008 to 0.010
SPECIFIC GRAVITY: 4.00
MOHS HARDNESS: 9
Sapphire is one of the Big 3 of jewelry gemstones—the other two are ruby and emerald.
Color The most highly valued blue sapphires are velvety blue to violet-blue, in medium to medium dark tones. Preferred sapphires also have strong to vivid color saturation. The saturation should be as strong as possible without darkening the color and compromising brightness.
Clarity Blue sapphires often have some inclusions. Blue sapphires with extremely high clarity are rare, and very valuable. Price can drop if the inclusions threaten the stone’s durability.
Cut To achieve the best overall color, maintain the best proportions, and retain the most weight possible, cutters focus on factors like color zoning, pleochroism, and the lightness or darkness of a stone.
Carat- Blue sapphires can range in size anywhere from a few points to hundreds of carats, and large blue sapphires are more readily available than large rubies. However, most commercial-quality blue sapphires weigh less than 5.00 carats.
Caring for your sapphire- Keep your sapphire beautiful by following simple care and cleaning guidelines.
Durability Corundum (ruby and sapphire) is relatively hard and tough; a great choice for daily worn jewelry.
CARE AND CLEANING Warm soapy water is always safe.
TREATMENT Fracture-filled, cavity-filled, or dyed material should only be cleaned with a damp cloth.
Sapphire Gemstone | Sapphire Stone – GIA. (2016, July 27). Retrieved July 27, 2016, from http://www.gia.edu/sapphire