How to Value a Diamond

The single most important piece of advice every diamond buyer should know:

Never purchase a diamond based upon certificate grades alone. Two diamonds with identical certificate grades are rarely equal in brilliance or value.

Example 1: The two diamonds below have identical GIA certificates:

Color: I         Clarity: VS1

Polish: Excellent         Symmetry: Excellent        Cut: Excellent

Why is diamond B approximately 20% more valuable than Diamond A?

Difference between EGL and GIA certificates

1.] Diamond 'B' has better proportion evident in the larger 'face size'.

Diameter Measurements: A = 7.41mm:   B = 7.58mm:

2.] Diamond 'B' is slightly whiter and more brilliant than 'A' even though both stones are graded GIA 'I' color.

Better and weaker examples of the same color grade is not unusual and must be taken into account when calculating correct value.

3.] The inclusions in diamond 'A' are located in the center (circled) whereas in diamond 'B' the inclusions are smaller and located towards the outside edge [circled bottom left].

Diamond 'B' is a more valuable example of a GIA, VS1 clarity grade.

At Ascot every diamond is scrutinized for brilliance, proportion and correct value before being added to our inventory; less than 5% of all diamonds produced meet Ascot's demanding standards.

Example 2:

In rare instances an EGL USA diamond may be more valuable than a GIA stone with the same grades:

The diamonds below have identical grades from the GIA and EGL:

Color I        Clarity VS1

We know GIA grades are stricter than EGL USA and therefore it would seem reasonable to assume that the GIA diamond is more valuable.

When we compare the 2 stones 'side by side' however, we see a different reality.

How to Value a Diamond

The GIA certified stone is considerably smaller than the EGL USA; clearly the GIA diamond has been cut to maximize weight rather than optimize 'face size' and brilliance.

The 'face size' on this GIA diamond is appropriate for a 1.75 carat rather than a 2.25 carat. Weight has been left on the underside of this diamond making it heavier but not larger where it matters [face size].

Please note GIA ‘Excellent’ grades for both Polish and Symmetry? Difficult to understand...

In contrast the EGL USA diamond on the right is beautifully cut, brilliant and has a face size that relates correctly to the carat weight.

A GIA certificate is no guarantee that a diamond is cut, graded or valued correctly. We advise diamond buyers to seek out a diamond company with the knowledge, reputation and skills essential to determine the brilliance and correct value for each stone.

We invite you to visit an Ascot Diamonds showroom where clients receive a priceless education and compare diamonds from 'the most carefully selected diamond inventory in the world'.

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