Pure Pearls Glossary
Lustre
How sharply a pearl reflects light. The single most important quality factor, and the one you can judge without any training.
Lustre is produced by light bouncing off and refracting through stacked layers of nacre. Thicker, better-aligned layers return a sharper reflection.
The test takes a second. Hold the pearl under a light source and look at the reflection. High lustre shows the light as a defined shape with crisp edges. Low lustre shows a soft smudge.
A high-lustre pearl with a few surface marks is a better pearl than a clean one that looks chalky. Lustre cannot be added later; surface marks can be hidden by a setting.
What you will hear
“A pearl that looks very bright and glassy in a listing photo has great lustre.”
In fact: Studio lighting flatters everything, and a thin-nacre saltwater pearl often looks glassiest of all. Sharpness of the reflected edge is the tell, not overall brightness.
When you are buying
If you only learn one thing about buying pearls, learn to check lustre. It survives photographs poorly, so judge it in person or ask for a video under a single light rather than a lightbox.
Read next
Nacre
The material a pearl is made of: microscopic aragonite platelets glued in layers by conchiolin. Thickness determines both lustre and lifespan.
Orient
The faint shifting rainbow that plays across the surface of a fine pearl, distinct from its lustre or its colour.
Pearl Grading
The A to AAA scale used to rate a pearl on lustre, surface, shape, colour matching and nacre. There is no global standards body enforcing it.
Surface Blemish
Pits, bumps, creases and dull patches on a pearl's surface. Some marking is present on essentially every pearl.
Not sure what you are being sold?
Paste any pearl description — another shop’s listing, a message from a jeweller, an old certificate — and we will break it down term by term.