EACH PEARL, WHETHER CULTURED OR NATURAL, IS TRULY INDIVIDUAL
The shape of a pearl will be largely due to the irritant that caused the pearl formation in the first place. This shape may subsequently be altered by:
- An organic substance that attaches itself onto the growing pearl. When this substance decomposes the gases released create internal blisters in the nacre layers. This effect produces protuberances in the pearl.
- A small pearl attaches itself to a larger pearl. The pearl sac surrounds both and continues to secrete layers of nacre.
- The change in water temperature and salinity can affect the pearl sac, which may tear and form marks on the pearl.
- A pearl while growing slides and is impeded by a muscle or organ in the molusc to grow regular layers of nacre due to the restricted space of its new surroundings.
- Pearls move and rotate while growing. A pointed object might constantly obstruct the pearl and this would produce a ringed or circled pearl, as the movement would have the same effect as that of moulding it on a potter’s wheel.
There are three main groups of pearl shapes: natural pearl shapes, cultured oyster pearl shapes and cultured freshwater pearl shapes.
SHAPES IN NATURAL PEARLS
The shapes in natural pearls can vary owing to the irritant, which caused the formation of the natural pearl in the first place, it could have been a large piece of grit, coral or shell, a worm or larvae, an infection or any manner of unwelcome guests or intruders against which the mollusc will need to defend itself or die. When natural pearls are found in strands they tend to be less closely matched in shape and colour tone due to their scarcity than their cultured pearl counterparts.
Shapes commonly found in Natural Pearls
SHAPES IN CULTURED OYSTER PEARLS
Unless we refer to the half-sphere found in the centre of a Mabe pearl, cultured oyster pearls have a large round portion in their bodies, where the mother of pearl or resin spherical nucleus is located within the pearl. This bead is the same irritant that is placed by the technician alongside the strip of epithelial cells into the pearl bearing oyster to start the cultured pearl formation. These pearls are termed nucleated. Cultured oyster pearls mainly produce just one pearl in their lifetime, the exception is Tahitian pearls which can produce two pearls at the same time.
Shapes found in cultured oyster pearls:
SHAPES IN CULTURED FRESHWATER PEARLS
Shapes in cultured freshwater pearls can vary from very flat and dispersed to round because of their cultivation process, which involves placing a piece of mantle containing epithelial cells from a donor mussel into the host mussel. These pearls are termed non-nucleated. The flexibility this cultivation process gives to the eventual formation of the pearl allows us to find literally any shape.
The mantle can be cut into a variety of shapes. Once the tissue has triggered the formation of a pearl sac, it produces a pearl, this pearl can be harvested, and the size of it depends on how long the pearl has been left to grow in the mussel. After the first harvest the mollusc is replaced into the water where the pearl sac will heal itself and produce another pearl, this can continue for up to three pearl harvests. This multiple harvest possibility in a mussel is important as in order to produce near perfect round potato shape pearls, freshwater pearls are harvested placed in a tumbling machine to make them perfectly spherical and then re-introduced into a mussel with an existing pearl sac which has just been harvested, thus ensuring a freshwater pearl that is a round as possible within the constraints of the molusc pearl producing organism.
The most common freshwater pearl shapes are: