Pearl Grading | Shape
Pearl Grading System
Pearl grading is very similar to the 4C's of diamond grading in that it takes into consideration several categories of qualitative comparisons. The pearl grading system consists of five main parts. They are:
2. Pearl Shape
Shape is one of the principle determining factors in a pearl's value. As a general rule, the rounder the pearl, the more valuable it is. Pearls come in a wide variety of shapes, each having a specific designation. Mabe, Baroque and Off-Round shapes have gained in popularity as the price of these irregular shaped pearls place them within the budget of a larger buying market.
A "round pearl" (A) is perfectly symmetrical and should roll in a straight line along a slightly angled surface. Only a small percentage of total pearl production will yield perfectly round pearls. This is because 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 nucleus is 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. Additionally, the pearl's positioning within the oyster also plays a role in determining its shape. If the pearl develops against the shell, for example, it will become more flattened on that side.
There are various terms to describe pearls that are "visually" round to the untrained eye, yet are slightly out-of-round. These terms are:
- Almost Round (B)
- Off-Round (C)
- Roundish (C)
All of these terms are used to indicate pearls that are "roundish" to varying degrees.
Other grading terms are used to describe pearls that are slightly to significantly out-of-round or which indicate an extended round shape but still look somewhat round. These terms are:
- Egg Round (D)
- Oval or Potato Shaped (E)
These pearls can appear to be round in photographs and perceived as round when the untrained observer is looking at the actual pearl. These would usually be covered in the Semi-baroque category.
Semi-Baroque Pearls
Semi-baroque (F) is a general term that typically describes shapes of pearls that are neither round or off-round and would include the following:
- Button Pearls
- Coin Pearls
- Drop Pearls
- Oval Pearls
- Peanut Pearls (Double Potato)
- Pear Pearls
- Rice Pearls
- Rondelle Pearls
- Stick Pearls
- Twin Pearls (Irregular Twins)
- Wheat (Firecracker) Pearls
Baroque is a general term that indicates a significant irregular shape. Typically these are the least expensive variety of pearls, yet certain specimens can be more valuable than perfectly round pearls. The baroque pearl can be abstract in its irregular shape, or it can resemble a stick, cross, or any number of other shapes.
Some baroque pearls develop with grooves or rings encircling them. These pearls are known as "ringed" or "circled" baroque pearls. "Stick pearls" (aka "Biwa pearls") are elongated, flat and narrow, and can be "center drilled" through the long dimension, or "top drilled" through one of the narrow ends. "Wheat pearls" (aka "firecracker pearls") are pear shaped, with a larger and smaller end.
Oval pearls are narrower at the ends than they are in the center. Ovals are categorized as a symmetrical shape. Button pearls or coin pearls are flattened, making them resemble a button or disk rather than a perfect sphere. Buttons are also categorized as symmetrical. Drop pearls are "pear" or "teardrop" shaped. These pearls make attractive earrings or pendants. They are also categorized as having a symmetrical shape.
Mabe Pearls
Mabe Pearls (aka blister pearls) are half-round pearls that are flat on one side. When the nucleus or foreign matter becomes fixed to the inside shell wall rather than in the oyster's body tissue, only the exposed portion becomes covered by the oyster's pearl-sac resulting in a blister pearl. Mabe pearls are grown in Silver-lipped and 'Mabe winged' pearl oyster.
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