THE FIVE VIRTUES
This most wondrous of gems emerge from the living oyster radiant with natural beauty. Unlike other gems, pearls require no cutting before being set into jewellery.
As a product of Nature, pearls occur in an infinite combination of shapes, colours and sizes making each pearl unique. After the harvest, each pearl is meticulously graded according to the following Five Virtues: Lustre | Complexion | Shape | Colour | Size.
1. LUSTRE
Lustre is the most important characteristic of a pearl. Of all precious gems, only pearls have lustre and it is this that gives pearls their singular beauty.
Luster is the amount of light a pearl reflects from both its surface glow and the deep mirror-like reflection of its inner light. The better the nacre quality of the pearl, the more superior its lustre. 
A pearl consists of countless layers of pearlescent organic material known as ‘nacre’. Lustre arises from the interaction of light with these layers of nacre.
The lustre of Australian South Sea pearls is attributable to the superlative quality and thickness of the nacre produced by the wild Pinctada maxima oyster. Together, these factors result in the lustre of incomparable radiance and iridescence.
A pearl with deep and radiant natural lustre is desirable and valuable whatever its shape, colour or size and despite any surface imperfections. Natural lustre is everlasting and should not be confused with the superficial metallic shine of treated pearls that may diminish over time.
2. COMPLEXION
A pearl with a flawless surface is exceptionally rare. A pearl’s quality is influenced by the number and size of imperfections and their degree of visibility. Clear, y noticeable imperfections compromise a pearl’s allure and value.
3. SHAPE
A pearl’s shape does not affect its quality. However, the demand for particular shapes does have a bearing on value. Round, teardrop, oval and button shapes are in especially high demand.
Some other shapes, such as circlé and baroque, are no less beautiful and have an appealing individuality. A circlé pearl features one or more grooved rings around the pearl. Baroque pearls are irregular in shape. These organic, free-form shapes can be very beautiful and lend themselves to exciting and creative jewellery designs.
Keshi pearls are in a category of their own. They are composed of pure pearl nacre and are generally baroque in shape. The term ‘keshi’ literally means ‘poppy-seed’ in Japanese and refers to the typically small size of these pearls. These beautiful gems account for less than one percent of the annual harvest.
4. COLOUR
Australian South Sea pearls are available in a wide array of natural colours mirroring the overtones of the Pinctada maxima shell in which they form.
Pearls vary widely in color based on the type of oyster that produces them. The rarer the shade, the more valuable the pearl. Colors range from cream, pink and grey to black, green and blue. White and pink rosé are among the most popular Akoya colors; peacock green and gold are among the rarest South Sea shades. While color choice is a matter of personal preference, always look for rich color, evenly distributed throughout the pearl.
5. SIZE
Australian South Sea pearls are the largest of all pearls, typically ranging from 11 to 16mm in diameter. Larger sizes up to 20mm and beyond are occasionally found and such pearls are highly prized.
While size does not affect the quality of cultured pearls, it does affect the price. Large pearls are more difficult to cultivate and their rarity makes them more valuable. Pearls are measured in diameter increments of millimetres (mm). The classic Akoya cultured pearl generally ranges from 3mm to 10mm. South Sea cultured pearls begin at 8mm and can grow as large as 18mm.