Sapphires are typically graded for quality based on several key factors that collectively determine their overall value. The following are the main criteria considered in the grading process:
- Color: Color is one of the most important factors in evaluating sapphire quality. The hue, tone, and saturation of the color are assessed. In blue sapphires, a vibrant and rich medium to medium-dark blue color with strong saturation is highly desirable. For fancy-colored sapphires, the intensity and purity of the color are evaluated. The presence of any secondary hues or color zoning within the gemstone can also affect its grading.
- Clarity: Clarity refers to the presence of internal characteristics, known as inclusions, and external blemishes in the sapphire. The clarity grade is based on the size, type, location, and visibility of these inclusions. Sapphires with fewer and less noticeable inclusions are considered more valuable. However, it's important to note that certain types of inclusions, such as tiny silk-like needles in a star sapphire, can enhance the gem's beauty and value.
- Cut: The cut of a sapphire determines its shape, proportions, symmetry, and overall craftsmanship. A well-cut sapphire maximizes its brilliance, sparkle, and color intensity. The quality of the cut is assessed based on the stone's light performance, faceting precision, and overall aesthetic appeal.
- Carat Weight: Sapphires, like other gemstones, are measured in carats. Carat weight refers to the size or weight of the sapphire. Generally, larger sapphires are rarer and command higher prices. However, the overall quality of the gemstone in terms of color, clarity, and cut is also crucial in determining its value, irrespective of carat weight.
- Origin: The origin of a sapphire can also impact its value and desirability. Certain locations, such as Kashmir, Burma (Myanmar), and Ceylon (Sri Lanka), are historically known for producing high-quality sapphires. Sapphires from these renowned origins may carry a premium in the market due to their exceptional color or historical significance.
Grading laboratories, such as the Gemological Institute of America (GIA) and the American Gemological Laboratories (AGL), provide detailed reports that assess these quality factors and assign grades to sapphires. These reports serve as a reliable reference for buyers and sellers in evaluating and pricing sapphires based on their quality characteristics.