Colour:

The four C’s that determine the value of a gem

Unlike diamond however, Sapphire is one of the Big 3 of jewelry colored gemstones—the other two are ruby and emerald.  Sapphires come in a wide range of colors, and each color has its own quality variations. In general, the more intense the color and the fewer the distracting zones of unattractive color, the more valuable the stone. Therefore we will take blue sapphire to describe the four C's.

Color has the most important influence on blue sapphire’s value. This is also affected by a gemstone’s hue, saturation and tone. Often, multiple colors can be found in the same sapphire. The most highly valued blue sapphires are velvety blue to violetish 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. Sapphires with these qualities command the highest prices per carat. 

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• Hue: is the gemstone’s basic color. While a sapphire’s color might be described as yellow or blue, more often gems are a combination of hues. For example, a blue sapphire can have violet or green secondary color components that affect their beauty and value. The hue of these sapphires would be more accurately described as violetish blue or greenish blue. 
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• Tone: which describes how light or dark a stone’s color is, will also influence a sapphire’s value. The preferred tones for sapphires vary from hue to hue, but most fine sapphires have a medium to medium-dark tone. For example sapphires that have a very dark tone are often described as “inky”. 
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• Saturation: describes how pure or intense a color appears, and it is a key component in determining a sapphire’s value. The color of a sapphire may be “diluted” with what is called a “saturation modifier.” With cool colored sapphires like blue, green, and violet , gray is the usual saturation modifier. With warm colored sapphires, including yellow, red, and orange , the typical saturation modifier is brown. Regardless of the sapphire’s hue, higher levels of saturation are preferred, which means their color is not diluted by modifiers. The finest sapphires have “vivid” saturation, but sapphires with “strong” saturation are also prized.
  

Clarity:

Sapphires host many different inclusions, and even the best stones are not expected to be inclusion free. A sapphire with no inclusions is often viewed with suspicion; it may be a synthetic stone or a glass imitation. The best clarity grade for sapphires is “eye-clean,” which means no inclusions are visible to the naked eye. When evaluating the clarity, experts consider the size, number, location, and overall visibility of the inclusions. Inclusions are a natural consequence of crystal growth. Sapphire inclusions vary with their source or origin and treatment history.

Generally, inclusions make a stone less valuable. Price can drop substantially if the inclusions threaten the stone’s durability. Even so, inclusions can actually increase the value of some sapphires. Many of the most valuable Kashmir sapphires contain tiny inclusions that give them a velvety appearance. They scatter light, causing the coveted visual effect without negatively affecting the gem’s transparency. 

Cut:

Gemstone’s proportion and finish.

Proportion refers to the rough dimensions and overall symmetry of a gemstone. Finish describes the precision with which facets meet, the relative size and number of facets, and the quality of the stone’s polish.

Like most transparent gems, sapphires reveal their full beauty when they are cut. However, because sapphire rough is so valuable, dealers and consumers accept gemstones without the precision cuts required of fine diamonds. In general, gem cutters follow four guiding principles when they fashion sapphires:

• Maximize the apparent color of the gem. A skilled gem cutter can influence the apparent color of the stone by maximizing a stone’s brilliance or amount of light returned to the viewer’s eye.
• Maximize the gemstone’s final weight. This may be constrained by the sapphire’s crystal habit or growth-form.
• Minimize the appearance of undesirable inclusions or color zoning.
• Filling consumer demand for certain fashions or cutting styles.

Carat Weight:

Large gemstones are harder to find than smaller ones. The effect of carat weight upon sapphire value varies from color to color. Yellow sapphires are comparatively plentiful in sizes above five carats, and extremely hard to be found with padparadscha sapphires. As with any gem, per carat prices increase with overall carat weight. Fine blue, pink, orange, or padparadscha sapphires that exceed fifteen carats are especially valuable and can fetch very high prices at auction.

All gemstone size, expressed in a unit of weight that is called a carat (abbreviated “ct”). A carat is a metric unit equivalent to one fifth (.20) of a gram. One hundredth of a carat is called a point (abbreviated “pt”). A number of small sapphires may be weighed together to give a total carat weight (abbreviated “tcw”). Because sapphires have a high specific gravity, a one-carat sapphire will appear smaller than a one-carat diamond.