SHAPE
Within each category of cultured pearls, the rounder the pearl the more valuable it is. Akoya cultivation tends to produce the roundest pearls. Only 5-10% of the Tahitian harvest is perfectly round making these pearls very expensive. Round freshwater pearls are relatively scarce compared to off-rounds.

SURFACE (BLEMISHES)
This refers to the degree of imperfections. Overly blemished pearls are discarded. In this case ‘less is more. The fewer the irregularities, the more valuable the pearl is.

COLOUR
Pearls come in an array of colours ranging from white to black and nearly all colours in between. Overall, no pearl colour is superior to another. However, depending on the pearl type, certain colours are rarer which in turn affects their value.

LUSTRE
The sharper the reflection of light on the surface, the better the lustre is. To judge lustre, imagine the pearl is a mirror and look at how sharp the reflections of light are on its surface. South Sea and Tahitian pearls tend to have a softer, more diffused lustre than Akoya pearls and are judged accordingly.

NACRE
Thickness is an important element of quality and affects durability. The nacre should never be so thin that the core nuclei can be seen. Thick nacre contributes to the durability, lustre and value of this gem.

MATCH
This describes how uniform all the quality factors are in a strand. All Birks pearl strands are carefully and individually matched - as are pearl earrings.