Beauty is in the eye of the beholder, and this is certainly true when it comes to Pearl shapes. Pearls are natural organic substances, they can occur in a wide variety of shapes, many of which are quite unique and interesting. The round pearls you most commonly seen and are by no means the only shape in which pearls are found!
Perfectly round pearls are actually quite rare. The eventual shape of the pearl is determined by a number of highly variable factors which occur inside the oyster as the pearl is developing. The pearl often assumes the same shape as its nucleus (the irritant which was placed inside the oyster to initiate the formation of the pearl). If the nucleus is not perfectly round, the resulting pearl is likely to reflect this irregularity. The pearl's positioning within the oyster also plays a role in determining its shape. For example If the pearl develops against the shell, it will become more flattened on that side.
There are three categories that pearl experts divide Pearls into, based on their characteristics:
v Spherical shapes are perfectly round or nearly round. They are the "classic" pearl shape that is most familiar and sought after.
v Symmetrical shapes are balanced and regular. If you sliced this pearl in half, each would be a mirror-image of the other half.
v Baroque shapes are irregular or abstract. They are non-symmetrical in nature. Every Pearl being unique in its irregular shape.
Within these three broad categories, pearls can be classified into seven basic shapes:
v Round: Round pearls are perfectly spherical -- the shape most people think of when they think of a pearl. Because of their relative rarity and "classic" nature, they are highly desirable. Round pearls fall into the spherical category.
v Near-Round: These pearls are not perfectly round. Instead, they are slightly flattened or elongated, rather than being a perfect sphere. Nonetheless, they are so nearly perfect that they, too, are classified as spherical.
v Oval: These pearls are shaped like an oval -- narrower at the ends than they are in the center. Ovals are categorized as a symmetrical shape.
v Button: Button pearls are flattened to some degree, making them resemble a button or perhaps a disk rather than a perfect sphere. These pearls are often used in earrings, where the flattened side can be attached to the setting. Buttons are also categorized as symmetrical.
v Drop: Drop pearls are pear or teardrop shaped. The drop can either be "long" or "short," depending on its proportions. These pearls make attractive earrings or pendants. This is also a symmetrical shape.
v Semi-baroque: These pearls are slightly irregular in their shape. For example, a pearl which might otherwise be considered an oval, button, or drop pearl, but which is not symmetrical in nature, would be considered semi-baroque. Semi-baroque pearls fall into the baroque category of shapes.
v Baroque: This is a pearl which is both non-symmetrical and irregular in shape. The baroque pearl can be purely abstract in its shape, or it can resemble a cross, stick, or some other shape.
Within these basic categories and definitions, there can be many variations. Some pearls, for example, develop with one or more grooves or rings encircling them. These pearls are known as ringed or circled. This adjective can be attached to the primary shape in order to more fully describe the pearl, such as "circled round" or "ringed oval."
The shape of the pearl is one of several factors which determine its Round and near-round pearls are the most valuable, because of their rarity. Symmetrical shapes are generally considered to be more desirable than baroque shapes. Baroques, however, can be extremely unique, thus increasing their desirability more than might be expected based on their shape alone.