Summary of the results
Diamond grading is not a science; it is a subjective skill. As mentioned, none
of the 17 diamonds in this survey was given the same grade for color and
clarity by all three laboratories. Due to the subjectivity of human color and
clarity grading, it is virtually impossible to say whether one or another grade
is absolutely accurate. Instead we decided to consider whether two of the labs
grades were stricter or softer compared to GIA-GTL grades. We made this
decision because GIA-GTL is the largest lab and is considered as a market leader.
To underline the subjectivity of diamond grading it is worth noting that stone #10
already had a 6 month old GIA-GTL report, but was inadvertently resubmitted to
GIA-GTL (it was to have been sent to for an AGSL report, which explains its
absence). The color was given the same grade, but the clarity on the GIA-GTL
report was VS1 on the earlier October 2003 report and VS2 on the April 2004
report. In discussions with the GIA about this particular stone they noted that
in their private records on both occasions that it was a border line VS1 / VS2.
The authors chose to include the stone at its softer GIA-GTL grading.
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