Where Does the Bead Inside a Pearl Come From? We Rewind Time | Rewind Factory #04
Short answer
- The bead inside a bead-cultured Akoya pearl is a nucleus made from shell.
- In this example, the bead makes up about two-thirds of the pearl by volume.
- GIA summarises that most nucleus shell came from freshwater mussels in the Mississippi and Tennessee river systems.
Also calledwhat is inside a cultured pearlwhat is a pearl nucleus made ofhow are Akoya pearls made
Video
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Explained
In the video
- 0:00What is inside a pearl?
- 0:28Unstringing and unsorting the pearls
- 0:48Back to a pearl farm in Japan (e.g. Ago Bay)
- 1:20Inside the oyster: the nacre comes undone
- 2:28A pearl cut in half: how big is the bead?
- 2:52A bead workshop in Japan: the bead turns back into shell
- 3:53The shell crosses the Pacific
- 4:33A freshwater mussel on an American riverbed
- 5:02Fast-forward back to the pearl
Inside an Akoya pearl grown in the sea in Japan sits a small bead made from another shell. Where did that bead come from? In the video we rewind a bead-cultured Akoya pearl — from the shop to a pearl farm in the sea in Japan, to a nucleus workshop in Japan (one example route), then back across the Pacific as a shell, to a freshwater mussel on the bed of a large American river.
The route
This is one example route. The shell species, origin, and supply route vary by product.
| Place | What happens there | When |
|---|---|---|
| A shop in Japan | The finished pearl jewellery | Today |
| A pearl farm in the sea in Japan (Ago Bay and similar bays, example) | The pearl inside its pearl sac, in an Akoya oyster | Between grafting and harvest (the period varies with conditions) |
| The farm, at grafting | A shell bead nucleus is inserted with a piece of mantle tissue | Before any nacre is laid down |
| A nucleus workshop in Japan (example, diagram) | Shell shipped to Japan is cut, rounded, and polished into a bead | A documented representative method; the country of processing varies by route |
| Crossing the Pacific (diagram) | One example route in which shell travels from America to Japan (the video rewinds it) | Routes vary by product; the two areas are roughly 10,000 km apart over the Earth's surface |
| A riverbed in the Mississippi and Tennessee river systems (United States) | Freshwater mussels (the washboard mussel is one example) | A typical source of nucleus shell |
What this episode shows
- A bead-cultured pearl is nacre laid down around a shell bead nucleus.
- GIA summarises that most shell for bead nuclei has been sourced from freshwater mussels in large American rivers.
- In this example, the bead inside makes up about two-thirds of the pearl by volume.
The numbers in detail
The cross-section ratio is a model calculation that treats both the finished pearl and the bead as perfect spheres. With an 8.0 mm pearl and a 7.0 mm bead, the nacre is 0.5 mm thick on each side, and the bead is about 67% (about two-thirds) of the volume. GIA gives 6.0–8.0 mm as the general range for nuclei, and a study in the Uwa Sea, Ehime, used a 6.67 mm nucleus. It varies by product.
Photo credits and licenses are listed to match the video description.
Sources
Where the facts and numbers in the video and on this page come from.
- GIA, “Pearl Description” (how bead-cultured pearls are made)gia.edu/pearl-description
- GIA, Gems & Gemology, Spring 2020, “Saltwater Bead Cultured Pearl with Laminated Nucleus” (general account of nucleus shell material and river systems; nuclei generally 6.0–8.0 mm)gia.edu/gems-gemology/spring-2020-labnotes-cult…
- Hubbs, “A Decade of Commercial Mussel Harvesting in Tennessee, 1992–2002,” Ellipsaria 7(1), p. 9 (Tennessee shells are shipped to Japan, China, and other countries, where they are cut and polished into beads)molluskconservation.org/PUBLICATIONS/ELLIPSARIA/Ellipsaria2005_…
- Cartier et al., “DNA Fingerprinting of Pearls, Corals and Ivory,” Journal of Gemmology 2018 (the washboard mussel is commonly used for nuclei, including Akoya)ssef.ch/wp-content/uploads/2018/09/2018-Cartier…
- Krumholz et al., “A Survey of the Commercially Valuable Mussels of the Wabash and White Rivers of Indiana,” Proceedings of the Indiana Academy of Science (shells cut into strips, squared, diced, then ground between two rotating discs with abrasive slurry until spherical — a documented representative method)journals.indianapolis.iu.edu/index.php/ias/article/download/7105/7147
- Tennessee Wildlife Resources Agency, “Fresh Water Mussels in Tennessee” (shell pieces cut, rounded, and polished into nuclei)tn.gov/twra/wildlife/fresh-water-mussels-in-te…
- Springer, “The Optical Characteristics of Cultured Akoya Pearl,” Fig. 12.1 (a 6.67 mm nucleus in a study in the Uwa Sea, Ehime)link.springer.com/chapter/10.1007/978-981-13-1002-7_12
- Illinois State Museum (the washboard has a thick shell, up to about 28 cm long)museum.state.il.us/ismdepts/zoology/mussels/gallery.html
- U.S. Army Corps of Engineers survey reporting (the Tennessee River joins the Ohio River, which joins the Mississippi; river lines on the map are drawn from Natural Earth data)apps.dtic.mil/sti/tr/pdf/ADA240265.pdf
- Radcliff, “Mussel Harvest and Techniques Used in Enforcement,” SEAFWA 45:495–499 (from the early 1950s, demand from Japan's cultured-pearl industry sustained the American shell trade)seafwa.org/sites/default/files/journal-articles/RA…
- Aerial footage of the Tennessee River: K (Pexels)pexels.com/video/scenic-aerial-view-of-tennessee-r…
- "Mucket (Actinonaias ligamentina)" by brettmeyer (CC BY 4.0)sketchfab.com/3d-models/mucket-actinonaias-ligamentin…
- "Threeridge" by atolin (CC BY 4.0)sketchfab.com/3d-models/threeridge-2aaf312b3ee842ae8f…
- "Mapleleaf" by atolin (CC BY 4.0)sketchfab.com/3d-models/mapleleaf-ed9e0332096d4095b16…
- "Pimpleback" by atolin (CC BY 4.0)sketchfab.com/3d-models/pimpleback-f660465853c04072ba…
- Photographs (modified): Ago Bay aerial photograph (2015), Geospatial Information Authority of Japan (GSI), GSI content terms (attribution). Cropped, with a slow camera push added. Sourcecommons.wikimedia.org/wiki/File:Ago_Bay_Aerial_photograph.201…
- “Pinctada fucata (Japanese pearl oyster) (Japan).jpg” (Akoya oyster shell) by James St. John, CC BY 2.0. Cropped, with a slow camera push added. Sourcecommons.wikimedia.org/wiki/File:Pinctada_fucata_(Japanese_pea…
- “Pinctada fucata (Japanese pearl oyster) (Japan).jpg” (Akoya oyster shell) by James St. John, CC BY 2.0. Cropped, with a slow camera push added. Source: https://commons.wikimedia.org/wiki/File:Pinctada_fucata_(Japanese_pearl_oyster)_(Japan).jpg Licensecreativecommons.org/licenses/by/2.0
- “Pearl Farm.jpg” (pearl-farm rafts, Ha Long Bay, Vietnam — shown as an example) by David Stanley, CC BY 4.0. Cropped, with a slow camera push added. Sourcecommons.wikimedia.org/wiki/File:Pearl_Farm.jpg
- “Pearl Farm.jpg” (pearl-farm rafts, Ha Long Bay, Vietnam — shown as an example) by David Stanley, CC BY 4.0. Cropped, with a slow camera push added. Source: https://commons.wikimedia.org/wiki/File:Pearl_Farm.jpg Licensecreativecommons.org/licenses/by/4.0
- “Naturalis Biodiversity Center - RMNH.MOL.326265 - Megalonaias nervosa” (washboard mussel shell specimen), Naturalis Biodiversity Center, CC0. Cropped to the shell, with a slow camera push and tracking ring added. Sourcecommons.wikimedia.org/wiki/File:Naturalis_Biodiversity_Center…
- “View of the Tennessee River Gorge from Julia Falls Outlook - 1 - June 2023.jpg” (Tennessee River) by Lazybookwyrm, CC BY 4.0. Cropped, with a slow camera push added. Sourcecommons.wikimedia.org/wiki/File:View_of_the_Tennessee_River_G…
Voice, music, art
- Music (OpenTracks): "時計図書館" by MATSU / "考え中" by 鷹尾まさき / "海底の神殿" by KK
- Sound effects (all CC0): simplewave "Tape recorder rewind (Fanmade)"; NearTheAtmoshphere "Whoosh"; Breviceps "River Rapids"; kyles "waves lake or ocean medium gentle splashing along low wall"; Kenney "Interface Sounds". The arrival bell and other sounds were made for this video.
- Voice: synthetic (Japanese: Irodori-TTS / English: Kokoro)
- Fonts: Zen Maru Gothic, Inter, M PLUS Rounded 1c (SIL Open Font License)
