Buying pearls can be confusing - there are many myths, misconceptions and misleading pieces of information (see Abuses of the Grading System below). One thing is certain. The romantic image of the pearl fisherman diving off the side of a small boat to harvest pearls from the ocean floor is gone. Wild pearls still exist but are difficult to find. Nowadays, pearls are cultivated in freshwater lakes and rivers or seawater rafts.
 


Lustre is one of the most important quality factors when buying pearls. Lustre refers both to the pearls brilliance - the way it's surface reflects light, and it's inner glow - the way it refracts light from the layers of nacre within. High-lustre pearls are bright with a deep glow. This usually means they have a thick coating of nacre. However, even thick nacre pearls may have poor lustre due to the way the mollusc secretes the substance. 



Surface Quality refers to the type and amount of blemish on a pearl. Most natural pearls have blemishes which separate them from imitation pearls.Unacceptable blemishes include holes or cracks in the surface, and flaking nacre. The cleaner the pearl, the higher it's value.
 


Shape  If you have read the section 'How Pearls are Formed' you will know that pearls develop into a variety of shapes. Traditionally, round pearls command the highest values but few pearls are perfect spheres.  
GRADE A AA AAA
Lustre Medium to Good Good to High High
Nacre Medium
(0.25-0.35mm) Medium to Thick
(0.35-0.5mm) Thick to Very Thick
(0.5mm+)  
Blemishes Light Slight Slight to Clean*
Shape Slightly off round
to round Slightly off round to
mostly round Round**
Matching Good Good to Very Good Very Good