Diamond Frequently Asked Questions

Diamond Cut

How is cut measured?

To determine a diamond's cut grade, an optical measuring device creates a three-dimensional model to determine the diamond's proportions and angles. The interrelations between these various dimensions will greatly affect how light reacts once it enters and how it behaves upon exiting the diamond. By using sophisticated computer modeling, it is possible to trace light behaviour and measure its levels of brilliance, fire and sparkle as it exits the top of the diamond, referred to as the face-up appearance by gemmologists.

Why is there no Ideal cut grade for the diamond shape I've selected?

The GIA and AGS have only applied ideal/excellent cut grade parameters to round brilliant stones at this time. When a GIA or AGSL cut grade is not available, Blue Nile provides a cut grade that allows you to compare diamonds using consistent criteria. Learn about the diamond proportional grading system Blue Nile uses to determine cut grade.

What's the difference between Ideal Cut and Blue Nile Signature Ideal Cut in round diamonds?

While both cuts are of a very high quality, the Blue Nile Signature Diamond conforms to the most rigid cut grading standards within the Ideal cut grade, ensuring these diamonds are the highest quality ideal cut diamonds you can find. Please read more about the special standards and criteria used to create a Blue Nile Signature Diamond.

What are polish and symmetry? How do they affect sparkle?

Polish describes the smoothness of a diamond's facets, and symmetry refers to the alignment of the facets. While polish and symmetry are worthy of noting, cut grade is far more important. Polish and symmetry can be helpful in choosing between two diamonds that are otherwise identical.

Diamond Colour

What is fluorescence and how does it affect the colour of a diamond?

Fluorescence refers to those diamonds that produce a visible reaction when exposed to ultraviolet radiation. In laboratory experiments with both trained gemmologists and individuals with no diamond experience (meant to represent the Jewellery-buying public), no relationship was found between fluorescence and a diamond's overall appearance. Diamonds with a strong or very strong fluorescence are a better value for the end customer because the market prices them slightly lower than diamonds with faint or negligible fluorescence.

What are "colored diamonds" and does Blue Nile offer them?

Coloured diamonds are an extremely rare, natural phenomenon of nature. If, while diamonds are being created deep inside the earth, they are exposed to certain trace elements, the result can be a coloured diamond in almost any hue of the rainbow. All Blue Nile coloured diamonds possess natural colour and are never exposed to artificial coloring techniques such as dyeing or irradiation. As with all Blue Nile loose diamonds, each coloured diamond is accompanied by a Gemmological Institute of America (GIA) report, which lists the diamond's specifications (e.g. colour grade) and natural origin.

Does clarity grade affect a diamond's sparkle and brilliance?

Clarity is a measure of the number and size of the tiny imperfections that occur in almost all diamonds. Because these imperfections tend to be microscopic, they do not affect a diamond's beauty in any discernible way. Thus, while the brilliance and sparkle of a well-cut diamond can help camouflage the imperfections of a diamond with a lower clarity grade, it is difficult to imagine a scenario where a diamond's imperfections are so large and prominent as to mar a diamond's sparkle and brilliance. Regardless, Blue Nile would never sell a diamond of such low clarity.

For a three-stone ring, should you keep the same color/cut/clarity parameters for the side diamonds?

For a three-stone ring, Blue Nile recommends that you choose the same cut grade for each of the diamonds, but colour and/or clarity can differ. For colour, there will not be a visible difference within three grades. For example, D, E, and F will each look the same. For clarity, anything VS2 or above will appear the same.

Diamond Certification

What is the difference between the AGSL and the GIA certificates?

The Gemmological Institute of America (GIA) and the American Gem Society Laboratories (AGSL) are among the most respected laboratories in the diamond industry. Both laboratories are highly respected due to their consistency and their conservative grading standards. There are minor differences in the terms that each lab uses to describe the qualities of the diamonds, but a certificate from either of these laboratories ensures that you have an accurate assessment of your diamond. Learn about the information included on the GIA certificate here, and learn about the AGSL certificate here.

Does Blue Nile carry diamonds certified by other laboratories, such as IGI or EGL?

The International Gemmological Institute (IGI) and the European Gemmological Laboratory (EGL) are two other independent diamond grading laboratories. Blue Nile does not carry diamonds certified by these laboratories.

What is a GCAL Report?

When you purchase a Blue Nile Signature Collection diamond, you will receive an additional certification from the Gem Certification & Assurance Lab (GCAL). This secondary certificate verifies that your diamond meets all the specific quality requirements of the Blue Nile Signature Collection, and provides you with an additional authoritative analysis of your diamond. The GCAL Diamond Certificate of Authenticity includes:

  • Actual Size Photo: A photo of your diamond at its actual size
  • Direct Light Performance Analysis: A visual image of your diamond's brilliance and optical symmetry
  • Laser Inscription Photo: A close-up shot of the laser inscription taken at 50x magnification
  • Proportion Diagram: A diagram noting your diamond's specific measurements, which are used to determine the cut grade.

In addition, GCAL offers a money-back guarantee that assures the accuracy of your diamond's grading. Learn more about the GCAL Certificate of Diamond Authenticity here.

Does Blue Nile offer an appraisal for my jewellery purchase?

Yes. An appraisal accompanies all diamond engagement rings, any jewellery set using our Build Your Own Diamond Jewellery feature, and most other jewellery over $1,000.