A pearl which has only been partly drilled, as for rings or stud earrings. These sell for more than those which are fully drilled. The best have a flawless domed side.
The term hallmark is often confused with branding, but it is not a branding. Hallmarking is a specific process of assaying precious metals and marking them as having passed a required standard. It is a guarantee of quality of content. Hallmarking dates, in England, from 1300 when Edward 1 brought in a requirement for standardisation of silver for coin and wrought pieces, which were to be marked with the leopard’s head mark to show they had passed assay. Variations on the leopard’s head are still used today for sterling silver pieces marked at the London assay office, run by the Worshipful Company of Goldsmiths. Different marks are used to denote fine silver, and the various grades of gold, plus platinum and palladium. A mark will show when and in which office the item was assayed, plus what metal and who made the item. The mark is either struck to the metal (the origin of ‘making one’s mark’ as the maker can optionally still strike their own sponsor’s mark before assay or the mark can be struck by laser. All Pearlescence precious metals over the required minimum weight carries the London Assay office hallmark of owner Wendy Graham (Initials wmg in an oval cartouche).
Pearls are harvested when the pearl farmer judges that there is enough nacre. This can either be cyclical or annual depending on the weather and the mollusc – in China the traditional harvests are in the winter as it is thought that winter nacre on the outside means a sharper and more intense lustre.
The harvest is also a time to seed the new crop, as the mantle tissue from the best producing pearls will be used to start the pearls for the next crop.
While some farms (eg Cortez and the Kamoka Tahitian pearl farm) market their own pearls as a name and brand in its own right, most pearls worldwide go into processing to be mixed with others to make strands at the processing factories. Some pearl sellers will claim that all their pearls come from the farm they visited, but this is extremely unlikely as one farm will not produce enough pearls to produce a range for retail.(and it is unlikely that a pearl farm will be able to drill and match for strands)
Tahitian pearl harvest.
The triangle shell is the shell used to culture most freshwater pearls in China
Irradiation Irradiation has differing effects from freshwater to salt water cultured pearls. The gamma rays do not affect the nacre layers of a salt water cultured pearl, but in fact darken the nucleus of the pearl. An irradiated salt water pearl appears to be grey or blue. The nacre of freshwater irradiated pearls, on the other hand, if affected by the gamma rays and can become very dark. Some of these freshwater treated pearls will also have an intense metallic sheen and iridescent orient over their surface.