What are the seven value factors?

The grading foundation comes from the GIA seven value factors: size, shape, colour, luster, surface, nacre quality and matching. Size and shape are obvious. Colour covers the body and its overtone. Luster is the sharpness of the reflection. Surface is how clean the skin is. Nacre quality is the depth and order of the layers. Matching is how well a strand agrees with itself.

Every honest grade is just these seven, weighed together. When you ask us why one pearl costs triple another of the same size, the answer is always somewhere in this list.

What AAA, AA and A actually mean

On top of the seven factors, the trade uses a letter scale. AAA is the top: high to very high luster, a surface that is at least 90 to 95 percent clean, a round or near-round shape, and even colour. AA is a clear step down, still attractive, with more visible surface marks or softer luster. A is entry level, where flaws are easy to see.

One warning: the letter scale is not policed by any single authority, so one seller's AAA can be another's AA. That is exactly why you should read the seven factors yourself rather than trust the letters alone.

Why luster outranks the rest

If you only learn to judge one factor, make it luster. A pearl with sharp, almost metallic luster looks alive across a room, and it forgives small surface marks. A pearl with chalky luster looks dead no matter how clean or round it is. At the grading table we sort on luster first, and everything else second.

Luster is also the hardest thing for a photo to fake, so when you shop online, ask for a video under daylight. A genuine high-luster pearl shows a tight, bright reflection of the light source. A soft, milky glow is the giveaway of a lower grade, whatever letter the tag claims.

The trade grade scale at a glance

Here is how the common letters line up against the factors that matter most. Use it as a quick map, then confirm with your own eyes under daylight. The same scale applies to Tahitian pearls and to South Sea pearls from Pinctada maxima, though a 14 mm South Sea round at AAA sits in a different price world from a 9 mm Tahitian at the same grade.

The factor you cannot see at a glance

Nacre quality is the one factor a quick look misses, and it decides whether your pearl lasts. A fine South Sea pearl carries 2 to 6 millimetres of nacre, which keeps its glow for decades. A thinly coated pearl can show the bead beneath within a few years. Ask about nacre depth, because a cheap pearl is often just a thin one.