Keep in mind that until the 1920s, most genuine pearls used in fine jewelry manufacture were indeed natural as opposed to cultured. One of the most important things to remember with natural pearls is that they will have a gritty feel to them when rubbed on your tooth. Over time, layer upon layer of nacre is naturally applied to the intruder by the host oyster or clam, and a pearl takes shape over a decade, give or take a few years. Natural pearls are those made when a foreign substance makes its way into the shell of a mollusk without any help-like the assistance they have when cultured pearls are farmed-from man. This is a skill that can be tackled at home, but it's wise to get some training from an expert as you're learning to make sure you don't overlook a piece made of valuable natural pearls. If the core is solid with no layering, then you know it is a cultured pearl. Jewelers can do this with a special scope inserted into the hole of a pearl, or by shining a light into the pearl and examining it with a jeweler's loupe. In order to determine whether a pearl is cultured, it must be examined for layers within resembling an onion. Imitation pearls will feel smooth to the tooth. One of the most important things to remember about cultured pearls in comparison to those made of glass or plastic with a thin coating of pearl finish used in costume jewelry is that they will have a gritty feel to them when rubbed on your tooth. This process usually takes several years with a cultured pearl whereas a natural pearl may take 10 or so years to form. Over time, in the same way that natural pearls are formed, layer upon layer of nacre is naturally applied to the intruder by the host mollusk.
Keep in mind that pearl culturing didn't really take root until the 1920s, so antique pieces dating prior to the Art Deco era are most often made with natural blister pearls rather than cultured.Ĭultured pearls are those made by inserting an object like a small bit of shell or even a bead into an oyster or clam. Other times they are mounted with the blister more clearly affixed to the shell base showing the natural contours, and sometimes imperfections, surrounding the blister. Sometimes they are isolated similarly to a mabe pearl. When fully formed, a blister pearl is cut away along with a portion of the shell. Cultured versions form around a nucleus glued to this inside of the shell and can vary in shape depending on the shape of the base material. These are usually less uniform in shape since the nucleus was not intentionally set.
Blisters occurring happen when a piece of mud or other substance serving as a nucleus attaches to the inside of a mollusk's shell. These pearls can be found in both fresh and saltwater mollusks, both naturally occurring and cultured, and they are part of the animal's shell rather than a true pearl. The brooch shown here features a blister pearl used as the centerpiece of an Art Nouveau brooch surrounded by enameling and diamond accents.