Analysis & Grading

GIA Facetware® Help



GIA Facetware Help

The Interface
Parameter Ranges
Proportion Parameters
Additional Factors
Abbreviations
Additional Information on Parameters and Output
Girdle Thickness
Girdle Min/Max
Painting / Digging
Polish and Symmetry
Total Depth
Why Facetware Results Differ from GIA Reports
Crown Height
Pavilion Depth
Total Depth
Affect On Cut Grade Estimate
Rounding In Practice


The Interface

1) Proportion parameters – required to estimate cut grade. Set to default values when Facetware® opens.
2) Additional factors - limits the maximum possible cut grade. Set to default values when Facetware® opens. For more information about the additional factors, download: Booklet - Finish, Culet, Girdle (high res).
3) Results – displays Facetware output values, including Estimated Cut Grade
4) Reset - returns all parameters to the default values that first display when Facetware® opens.
5) Add Your Parameter Set - creates a temporary list of your input values and corresponding results. Name each parameter set and click “Add” to create the list. List is valid for your current session only.
6) Displays saved parameter sets.
7) Select All – highlights all the sets in your list.
8) Delete – removes selected sets from your list.
9) Email – opens email client to send the selected sets in your list.
10) Print – prints selected sets in your list.
11) Export – converts selected sets in your list to a CSV file.

Back to Top


Parameter Ranges

Proportion Parameters

Parameter Low High Increment
Table Size 44% 72% 1%
Crown Angle 20° 41.5° 0.5°
Pavilion Angle 37.2° 43.8° 0.2°
Star Length 35% 75% 5%
Lower Half 60% 95% 5%
Girdle Thickness 1.5% 11% 0.5%

Additional Factors

Parameter Values
Girdle Min ETN, VTN, THN, MED, STK, THK, VTK, ETK
Girdle Max ETN, VTN, THN, MED, STK, THK, VTK, ETK
Culet Size NON, VSM, SML, MED, SLG, LGE, VLG, ELG
Polish EX, VG, G, F, P
Symmetry EX, VG, G, F, P
Painting/Digging NEG, MOD, SIG, SEV

Abbreviations

Abbreviation Full Name
ELG Extremely Large
ETK Extremely Thick
ETN Extremely Thin
EX Excellent
F Fair
G Good
LGE Large
MED Medium
MOD Moderate
NEG Negligible
NON None
P Poor
SEV Severe
SIG Significant
SLG Slightly Large
SML Small
STK Slightly Thick
THK Thick
THN Thin
VG Very Good
VLG Very Large
VSM Very Small
VTK Very Thick
VTN Very Thin

Back to Top


Additional Information on Parameters and Output

Girdle Thickness

The range displayed for Girdle Thickness (percentages) varies with the choices for Girdle Min and Girdle Max (verbal descriptions). These three parameters describe different aspects of the round brilliant's scalloped girdle. Girdle Thickness is measured at the eight junctions between the bezel and pavilion main facets, and expressed as a percentage of the average diameter. It describes the distance between the crown and pavilion of the round brilliant. Girdle Min and Girdle Max (verbal descriptions) are assessed in the "valleys" between the upper and lower half facets. Typically the girdle thickness percentage in these valleys is about 1.7% less than the girdle thickness percentage measured at the bezels for normal proportions and when no or negligible painting or digging is present. Characteristics like naturals and cavities can affect the reported descriptions of Girdle Min and Girdle Max (see Booklet - Finish, Culet, Girdle (high res), pages 8 and 9).

Girdle Min/Max

The Girdle Min and Girdle Max values (along with the other additional factors) combine to potentially limit the maximum possible cut grade. Facetware opens with Girdle Min and Girdle Max both set to MED, which causes Girdle Thickness to show a range from 2% to 5%, at 0.5% increments. Changing Girdle Min to ETN changes the Girdle Thickness range to 1.5% - 4.5%. Alternatively, changing Girdle Max to ETK yields a range of 4% - 11% for Girdle Thickness choices. If the desired Girdle Thickness value is not displayed, try changing either Girdle Min or Girdle Max by a few settings to extend the range.

Once the desired value for Girdle Thickness has been chosen, set the values for Girdle Min and Girdle Max, and check that these choices did not force a change to the Girdle Thickness value. For the rare cases where the correct Girdle Min or Girdle Max is not compatible with the desired value of Girdle Thickness, find the estimated grade for the correct proportion combination. Then see page 5 of Booklet - Estimating a Cut Grade, to apply further limitations from the actual Girdle Min or Girdle Max value.

Painting / Digging

The effect of painting or digging out to the cut grade can be applied at four levels: negligible, moderate, significant, or severe. Use this factor to determine whether moderate or stronger painting or digging would limit the estimated cut grade based on the proportions. An explanation and visual presentation of the different forms of painting and digging can be found in the PDF: Booklet - Finish, Culet, Girdle (high res).

Polish and Symmetry

Polish and Symmetry are graded according to descriptions that can be found in the PDF: Booklet - Finish, Culet, Girdle (high res).

Total Depth

The total depth percentage displayed in the output is calculated from the combination of rounded proportion parameters. This calculated value may differ from the reported total depth percentage, which is based on the measured diameter and depth of the diamond.

The calculation of total depth percentage includes the chosen culet size. The default culet size is VSM, and total depth limits (as described on page 5 of the pdf Booklet - Estimating a Cut Grade) are applied to calculated total depth with this default size. Culets of MED and larger limit the initial cut grade based on the proportions.

Back to Top


Why Calculated Facetware Results May Differ from GIA Reports

Facetware® has access to the six rounded proportion parameters selected by the user. When the Laboratory grades a round brilliant diamond, more than 100 individual measurement values are gathered and processed. In some cases, these distinctions lead to rather different values for crown height percentage, pavilion depth percentage, and/or total depth percentage, as described below.

Crown Height Percent

The crown height percentage displayed in Facetware® may differ from the value printed on the report. For GIA Diamond Grading and Diamond Dossier® Reports, crown height is measured at the eight bezel facets. These eight measurements are then averaged and converted to a percentage of the average diameter. The resulting number is rounded to the nearest 0.5%. Facetware® calculates crown height according to this formula, using rounded table percentage and rounded crown angle: Crown Height % = 0.5 (100 - Table %) x TAN (Crown Angle Average). The resulting number is rounded to one decimal place.

Pavilion Depth Percent

The pavilion depth percentage displayed in Facetware® may differ from the value printed on the report. For GIA Diamond Grading and Diamond Dossier® Reports, pavilion depth is measured at the eight pavilion main facets. These eight measurements are averaged, converted to a percentage of the average diameter, and rounded to the nearest 0.5%. Facetware® uses culet size and rounded pavilion angle to calculate pavilion depth according to this formula: Pavilion Depth % = 0.5 (100 – Culet Size %) x TAN (Pavilion Angle Average). The resulting number is rounded to one decimal place. A specific value is used in this formula for each verbal culet size; very small corresponds to 0.5%.

Total Depth Percent

The total depth percentage displayed in Facetware® may differ from the value printed on the report. For GIA Diamond Grading and Diamond Dossier® Reports, total depth percentage is based on the measured diameter and depth of the diamond. The total depth percentage displayed in the Facetware® output is calculated from the combination of rounded proportion parameters, according to this formula: Crown Height % + Pavilion Depth % + Girdle Thickness %, where crown height and pavilion depth percentages are derived from the calculations mentioned above. This calculated value may differ from the reported total depth percentage; typical differences are 0.2 – 0.3%, with extreme cases differing by as much as 0.8%.

Affect On Cut Grade Estimate

For round brilliant diamonds with girdle thickness between 2.5 and 7.0%, the six rounded proportion parameters in the input section determine the Facetware® estimated cut grade, just as those parameters produce the first component of the cut grade within the GIA laboratory. The chosen culet size affects the calculated values of pavilion depth and total depth percentages, but neither of those displayed values, nor the reported total depth percentage, are part of the estimated cut grade. Within this girdle thickness range, total depth percentage was calculated for all proportion combinations in the grading system using a default culet size of 0.5% (very small) to produce the limits shown in the figure below and at Booklet - Estimating a Cut Grade.

The Facetware® cut grade estimator does not include limitations based on the total depth percentage for girdle thickness outside this range (less than 2.5 or larger than 7.0%). Facetware® warns users that grade estimates are subject to additional grading limitations. For round brilliants with girdles less than 2.5%, the final cut grade assigned by GIA may be higher than estimated using Facetware®. For round brilliants with girdles larger than 7.0%, comparing reported values of total depth and girdle thickness to the limiting factor borders usually produces an accurate grade estimate.

Please use the Feedback form if you would like assistance applying total depth limits for a particular example.

Rounding In Practice

Facetware® uses rounded proportion parameters selected by the user to calculate values for crown height, pavilion depth, and total depth percentages, each of which may differ from the value printed on the report. For round brilliants with average girdle thickness between 2.5 and 7.0%, measured total depth plays no role in the cut grade. Instead, total depth is calculated from those six averaged parameters, according to well-known formulas described below. The grading system uses calculated total depth in order to achieve and maintain predictability, an essential aspect of the system for manufacturers.

Let’s look at an example where the measured values differ from the calculated values and how that impacts the cut grade.

This 5.00 carat round brilliant received a Very Good cut grade by the GIA laboratory. The reported total depth based on measurements is 65.2%, as shown on this profile image. The Facetware® calculated total depth is 64.5%, which can be derived by the following formulas:

Crown Height % = 0.5 (100 - Table %) x TAN (Crown Angle Average)
= 0.5 (100 – 53) x TAN (35.5)
= 16.8%

Pavilion Depth % = 0.5 (100 – Culet Size %) x TAN (Pavilion Angle Average)
For girdle thickness between 2.5 and 7.0%, a default value of 0.5% (very small) should be used for the culet size.
= 0.5 (100 – 0.5) x TAN (41.0)
= 43.2%

Total Depth % = Crown Height % + Pavilion Depth % + Girdle Thickness %
= 16.8 + 43.2 + 4.5
= 64.5%

This is a case where the reported total depth differs from the Facetware® calculated total depth by 0.7%. This favorable rounding keeps the total depth parameter in the Very Good range.

Total Depth % Limits
Excellent 57.5 - 63.0
Very Good 56.0 - 57.4  or  63.1 - 64.5
Good 53.0 - 55.9  or  64.6 - 66.5
Fair 51.0 - 52.9  or  66.6 - 70.9
Poor ≤ 50.9  or  ≥ 71.0

Proportion combinations too close to the rounding boundaries and grade borders can lead to unfavorable rounding as well, which ultimately impacts the cut grade in a negative way.


 

This 0.54 carat round brilliant received a Very Good cut grade by the GIA laboratory. The reported total depth based on measurements is 62.6%, as shown on this profile image. The Facetware® calculated total depth is 63.1%, which can be derived by the following formulas:

Crown Height % = 0.5 (100 - Table %) x TAN (Crown Angle Average)
= 0.5 (100 – 57) x TAN (36.0)
= 15.6%

Pavilion Depth % = 0.5 (100 – Culet Size %) x TAN (Pavilion Angle Average)
For girdle thickness between 2.5 and 7.0%, a default value of 0.5% (very small) should be used for the culet size.
= 0.5 (100 – 0.5) x TAN (40.8)
= 42.9%

Total Depth % = Crown Height % + Pavilion Depth % + Girdle Thickness %
= 15.6 + 42.9 + 4.5
= 63.1%

This is a case where the reported total depth differs from the Facetware® calculated total depth by 0.5%. This unfavorable rounding pushed the total depth parameter down one grade into the Very Good range.

Over time, manufacturers have learned how to make use of the rounding rules to produce both high cut grades and higher weight yield, resulting in a number of grading reports where the reported total depth percentage (as measured) noticeably exceeds the published limit of 63.0% (as calculated) for an Excellent cut grade. However, as shown above, cut planning so close to both rounding boundaries and grade borders assumes the risk that one parameter will round unfavorably and produce a proportion combination with a lower cut grade.

Minor differences in measured total depth can also be attributed to the precision of the measuring device, and the subsequent precision used in averaging those measurements. For instance, the GIA laboratory takes the average of multiple unrounded measurements, and then rounds the averaged number. If the measuring device is using lower precision than by those used at GIA, one or more parameters may round differently. In that case, the imbedded Facetware® grade estimator in your device may give a different grade than the report, along with at least one parameter reported differently.

Back to Top

GIA Facetware

Use Facetware to access GIA's database of more than 38.5 million proportion sets and estimate
a cut grade.

Log In

Free Facetware App

Visit www.gia.edu/facetware-mobile with your iPhone or Android phone.

Cut Grading System Charts & Booklets

Read More

You Might Also Like

Find a Retailer
learn more
Shop the Campus Store
Learn More
Quality Assurance Benchmarks
Learn More
Summer 2017 Gems & Gemology
G&G Summer 2017 Edition
Learn more