Pure Pearls Glossary
Tissue Nucleated
Grown around a scrap of mantle tissue instead of a bead, so the pearl is solid nacre throughout. The freshwater method.
A technician inserts a small piece of donor mantle tissue into the mussel. The tissue forms a pearl sac and the mussel fills it entirely with nacre.
With no bead inside, the pearl cannot be sliced open to reveal a core, and nacre thickness stops being a meaningful risk.
The trade-off is shape. Without a round bead to grow on, perfect roundness is far harder to achieve, which is why round freshwater pearls command a premium over oval and semi-round ones.
When you are buying
This is the strongest technical argument for freshwater pearls. A tissue-nucleated pearl cannot lose its nacre layer, because it is nacre all the way down.
Read next
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.
Nacre
The material a pearl is made of: microscopic aragonite platelets glued in layers by conchiolin. Thickness determines both lustre and lifespan.
Freshwater Pearl
A pearl grown inside a mussel in a river or lake, rather than an oyster in the sea. Most pearl jewellery sold today is freshwater.
Keshi Pearl
A pearl that forms by accident with no nucleus at all, so it is solid nacre. Irregular in shape and unusually bright.
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.