Color Is The Most Important Quality Factor For 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.
Clarity Refers To The Inclusions
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. Kashmir sapphires contain tiny inclusions that impart a desirable velvety appearance.
Cut Is One Of The Most Important Factors In Appearance
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 Weight Allows For Precise Measurements
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.
Reference GIA Buyers Guide