How to Rate a Sapphire

Examine the color of the sapphire. The hue defines the combination of more than one color in its structure. The best hue is a solid, even base color rather than a mixture of colors. The tone of the sapphire describes its lightness or darkness. The highest-rated sapphires have a medium to medium-dark tone rather than a tone that is too pale or so dark that the color is hard to define. The highest-rated base color for a sapphire is a deep or royal blue that does not shift under angled light.

Look for even and pure color saturation. Some sapphires appear diluted (multiple colors) with a saturation modifier. Green, blue and violet sapphires, the cooler colors, have a gray saturation modifier. Red, yellow and orange sapphires have a brown modifier. For example, an orange sapphire with weak saturation would be called a brownish orange specimen because the color shift is definable inside the gem. The modifier is the base color and should not appear with other lighter or darker shades, giving it a two-tone color effect. The best-rated sapphires have very strong or vivid saturation, one even color throughout. Color zoning means that the color lacks uniformity and appears uneven within the gem.

Look for inclusions, or imperfections inside the gem. Sapphires can contain a number of inclusions stemming from natural crystal growth. Rating inclusions involves determining their size, location and number or frequency. Use a 10X magnification loupe to examine the gem. Look for abnormalities such as holes or cavities, small pressure cracks or feathering cracks, fingerprint-type tubes and tiny minerals trapped inside the gem.The best-rated sapphires are termed "eye-clean," which means that no visible inclusions can be seen with the naked eye. A few minor inclusions will not distract much from a sapphire's value. Haphazard, or scattered inclusions detract from the value.

Examine the cut of the gemstone under magnification. Look for evenly cut facets, the flat faces of the gem. The edges of the cuts should be sharp and well-defined. Look for clarity of each facet, the number of facets and the polish of the exterior surface. Note the gem's cut length, the thickness of the gem from top to bottom. If the cut length is too deep or shallow, it hampers the brilliance. Look for a medium or "well-cut" gem that accentuates the color and brilliance. Look for facets that have the same profile, length and width over the entire gem. The highest-rated sapphires have perfect facet cut and balance.

Weigh the sapphire on a professional gem scale, which indicates weight in carats. A carat is 0.20 grams. Generally, the larger the number of carats, the more valuable the gem, even in rough or raw form. Padparadscha sapphires and deep blue and royal blue colors are the most valuable per carat. Yellow sapphires and other off-colored gems are plentiful in large carat sizes and do not have high values for their carat size.

Determine the country origin of the sapphire. You might need the assistance of gemologist to determine this. Generally the highest-rated sapphires come from Kashmir, followed by Myanmar and Sri Lanka. Sapphires of exceptional quality from other countries are still highly valuable.

Take the sapphire to a dealer with a certified gemologist on its staff. You can obtain a Colored Stone Grading Report, which will indicate value numbers, word descriptions and percentages related to the gem for an overall grading report. Such a report includes shape and cut, color grade, finish grade, carat weight and Total Integration Rating. The report also list sub-categories that further define a gem's characteristics.