The GIA Colored Diamond Grading Report - a User's Guide (Part 2)
In a previous article - GIA Certification of Colored Diamonds – background was provided of the Gemological Institute of America and the GIA Colored Diamond Grading Report. This article is the 2nd section of the GIA Colored Diamond Grading Report, User's Guide and should be an integral part of buying a colored diamond as it affords buyers the security and peace of mind that they are buying a stone that has been objectively appraised by one the most reputable authorities in the diamond industry.
Beneath the General Information is the Grading Results, which include the following data:
• Carat Weight – diamonds are weighed in carats. A diamond’s carat weight is measured to the nearest 1/1000 of a carat but rounded to the nearest 1/100 of a carat. A carat equals 1/5 of a gram.In the sample above, the carat weight is 1.22 carats. This means that the carat weight fell in the range of 1.085 – 1.089 carats.
- Color– information pertaining to color is classified according to Origin, Grade, and Distribution.
- Origin – states whether the diamond’s color is natural or treated. Occasionally, it will be impossible to ascertain the origin of color, in which case the diamond will be reported as “Undetermined.” In the sample above, the origin is natural.
- Grade– one of the more complex categorizations for color diamonds, color grade is a combination of hue, saturation and tone. Hue refers to the color, saturation to the intensity of the color, and tone to the shade.
- Hue – this is the dominant color of the diamond, i.e. pink, green, red. A maximum of four hues can be listed under a diamond’s color. There is generally acknowledged to be 27 hues of fancy color diamonds.
- Saturation – this is the strength or intensity of a diamond’s color. Logically, strong saturation results in a richer hue and vice versa. If the stone has a dark color tone, the saturation can vary from dark to deep. If the stone is light in tone, the saturation can vary from pastel to vivid and intense. In the sample above, the grade is Fancy Intense Yellow.
- Tone – this describes how light or dark the stone appears to retain when illuminated – the higher the tone, the darker the color. Tone ranges from very light to very light or dark to very dark.
- Distribution – this refers to the evenness of distribution of color throughout the diamond when viewed face-up using standard viewing procedures. The greater the distribution, the better. Distribution is categorized as “Even” – symmetrical in over 50% of the stone, “Uneven” – asymmetrical in over 50% of the stone, or “Not Applicable” for the grades faint, very light, and light. In the sample above, the distribution is Even.
- Clarity Grade – this assesses the relative absence of inclusions (internal characteristics) and blemishes (external characteristics) of a diamond. There are 11 clarity grades on a scale from the highest grade of Flawless (FL) to the lowest grade of Included (I – graded on a scale of 1-3, with I3 being the lowest). Clarity grade is based on the size, nature, number, position, and relief of characteristics visible under 10x magnification.In the sample above, the clarity grade is VS1 the second highest grade after Flawless. A copy of the Clarity Scale is provided on the report (see Scale References).
Learn More About Diamond Clarity
Additional Grading Information
Beneath the Grading Results is the Additional Grading Information, which includes the following data:
- Finish – information pertaining to finish is classified according to Polish and Symmetry. This is the value added to the diamond by the cutter and his art.
- Polish – this is the overall condition or smoothness of the diamond’s surface, i.e. how carefully the stone has been polished and whether any surface imperfections are sufficient to affect the clarity grade. Polish is assessed according to five levels on a scale from Excellent to Poor. In the sample above, the polish is Very Good.
- Symmetry – this is the proportion of the diamond’s outline as determined by the shape, placement, and facet alignment. Two types of symmetry are considered – proportion symmetry and facet symmetry.
- Proportion Symmetry – this is the configuration and equilibrium of the diamond’s table, culet, angles, and girdle, i.e. the external parts of the diamond
- Facet Symmetry – this refers to the shape, placement, and presence or absence of facets.
Symmetry is also assessed according to five levels on a scale from Excellent to Poor. In the sample above, the symmetry is Good.
- Fluorescence – this measure is deemed to be of little value when assessing the value of a colored diamond and used mainly for identification purposes. Fluorescence measures the strength and color of a diamond when viewed under short or long-wave ultraviolet light. Fluorescence is assessed according to five levels from “None” to “Very Strong”, with “Strong” and “Very Strong” being less preferred.
In general though, pink diamonds have a stronger tendency to fluorescence than other colors. Consequently, a strong fluorescence grade for a pink diamond won’t adversely affect its value. This can be contrasted with yellow diamonds which have very faint or no fluorescence. Consequently, yellow fluorescence in a yellow diamond intensifies the stone’s color. This also applies to green and orange diamonds with matching color fluorescence.
In the sample above, the fluorescence is None.
- Comments – include additional identifying features or characteristics not otherwise represented on the report but that the grader thinks is relevant.