Pure Pearls Glossary
Nacre
The material a pearl is made of: microscopic aragonite platelets glued in layers by conchiolin. Thickness determines both lustre and lifespan.
A mollusc lays down nacre in sheets thinner than a wavelength of light. Light passing through and between those sheets interferes, which produces both the depth of lustre and the rainbow flash called orient.
In a bead-nucleated saltwater pearl, nacre is a coating over a shell bead and can be as little as 0.3mm. In a tissue-nucleated freshwater pearl it is the whole pearl.
Thin nacre is visible as a slightly blue, glassy cast, and sometimes as a faint banding under strong light where the bead shows through.
When you are buying
Nacre thickness is the durability question. A thick-nacre pearl can be re-polished decades from now. A thin-nacre one wears through and cannot be repaired.
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Lustre
How sharply a pearl reflects light. The single most important quality factor, and the one you can judge without any training.
Orient
The faint shifting rainbow that plays across the surface of a fine pearl, distinct from its lustre or its colour.
Bead Nucleated
Grown around a round shell bead, so the pearl is a nacre shell over a core. The saltwater method, and how roundness is achieved.
Tissue Nucleated
Grown around a scrap of mantle tissue instead of a bead, so the pearl is solid nacre throughout. The freshwater method.
Peeling
Nacre lifting or flaking away from a pearl, exposing the bead beneath. Terminal, and caused by thin nacre or chemical damage.
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.