Keshi (ケシ), meaning poppy seed in Japanese, was originally used in Japan for very small-sized natural pearls, namely the very rare Akoya natural pearls that were locally collected until the early 20th century. Today, however, the original meaning of the word "keshi" became corrupted and is now a trade name for the nacreous non-bead saltwater cultured pearls that form, by accident or intentionally, inside pearl producing molluscs as a by-product of the classic seeding or grafting process. The first reported cultured keshi pearls in the early-20th century were associated to the then emerging Akoya cultured pearl farming in Japan and now "keshis" are are also found elsewhere and in other nacreous pearl producing molluscs (e.g. South Sea, Tahitian). Distinguishing non-bead cultured from natural pearls is very complex, requiring lab experience and modern tools - real-time X-ray microradiography (RTX) and X-ray computerised tomography (µ-CT), and often results in different interpretations. In the image, the Rockpool Styarfish Cuf by Paspaley featuring South Sea keshi cultured pearls gathered over four annual harvests, showing the exceptional character of these rare nacreous biogenic gems that are discovered in very small quantities each year .

Source: Rui Galopin de Carvalho. (Portugal Gems Academy)

Mother-of-pearl has been used since pre-historic times for adornment. In the modern ages, it was also artistically used in marquetry, gaming chips, devotional artefacts, as a bead for the cultured pearl industry but also in the button industry, being rather popular before plastics came into action. Mother-of-pearl is the smooth nacreous iridescent coating on the interior of some molluscs and Pinctada maxima, the Australian South Sea pearl oyster (also known as pearl button oyster and mother-of-pearl oyster) has been a rather important source not only for the quality of the nacre but also because the wild shells have notorious sizes averaging between 20 and 30 cm, up to 40 cm in exceptional cases. Although local shells in the north have been collected since pre-history, the pearling industry only started in Australia in 1868, especially in Queensland. In the photos, a pearl shell sorter in Thursday Island, Queensland, Australia. Photo Frank Hurley © National Library of Australia ; and a series of Pinctada maxima shells being manufactured as buttons, from the Museum of Applied Arts and Sciences‬ collection (B&W picture from 1933 at the The Pearlbutton Manufacturing Co. Ltd in Sydney, New South Wales, Australia). ‪

Source: Rui Galopim de Carvalho (Portugal Gemas Academy)