Pearl shapes are spherical, symmetrical or non-symmetrical. Usually, the spherical pearls (rounds and semi-rounds) are the most valued. However, choice of shape is a matter of personal taste and preference. Symmetrical shapes include circles, drops, ovals and buttons, whereas the non-symmetrical shapes comprise irregularly shaped pearls known as baroque and semi-baroque.
- Round and Semi-round (R/SR) - the pearl is spherical in shape or near to it.
- Symmetrical shape (Drop Oval or Button) - the pearl has at least one line of symmetry.
- Drop (includes Pear and Cone)
- Semi-baroque (SBQ) - the pearl has at least one line of symmetry with off-round slightly irregular oval, button or drop shape.
- Baroque (BQ) - the pearl is non-symmetrical, irregular or freeform in shape which do not fall into any of the above categories.
- Circle (CIR) - A Circle pearl has one or more concentric rings or circles that are indented and in the shape of a groove around its circumference regardless of its original shape.
- Exception - when the rings are located only within 30% of either the upper or lower end of the pearl along its vertical axis, the pearl is classified in the category of its original shape without taking intoaccount the rings.
In the Cook Islands, Pinctada Margaritifera pearls tend to range on average between 9 and 13 millimetres with the very occasional pearl reaching 18 millimetres.