Pearl Grading

Luster

Pearl luster is best described as the pearls natural ‘glow’.  Luster is any gem’s surface appearance in reflected light.  Pearl luster can range from dull to almost metallic and can range depending on the type of pearl you are dealing with.

Better quality Akoya pearls can have an excellent mirror like luster while top quality South Sea Pearls will have a satiny glow.  The reasoning for this is the water temperature during the formation of the pearl.  Akoya pearls are farmed/harvested in colder waters contributing to a higher luster.  South sea pearls are warm water pearls which gives the pearls a ‘softer’ more internal glow.

Top quality Tahitian pearls will have an almost metallic luster. Freshwater pearls can display all luster qualities from dull to excellent.

 

Complexion

The complexion of a pearl is more commonly referred to as ‘Surface Quality’.  It describes the visual characteristics on each pearl such as chips, nic’s, cracks, wrinkles, color concentrations – or lack thereof.

Pearls that have very few to no surface characteristics are more desirable and of higher overall quality than those that have dominant or many surface characteristics.  Crack’s and chips in pearls will sometimes affect the durability of your gem so this is something that should be addressed with a professional. Some surface characteristics, however, are what make your pearls individual and unique.

 

Color

Pearl color ranges from the whitest of white to the darkest of black and every color in between.  Depending on the variety of pearl you are dealing with, there are a range of common colors, overtones, and possible colors which are now available due to common treatments.

Akoya pearls are most desired in white with a rose overtone.  Blue and Green overtones are also common, and the pearls body color can range from white to cream.

Tahitian pearls are commonly referred to as ‘Black’ pearls.  Tahitian’s come from the ‘Pinctada margaritifera’’ oyster – also known as the ‘Black-lipped oyster.’  Typically the body color produced by this oyster can range from a light silver-grey to a black and may display weak to strong overtones.  Pistachio (green), Peacock (blue/turquoise), and Aubergine (deep purple) are the most desired and recognized overtones of these south pacific pearls.

South Sea Pearls, like Tahitian’s, get their color from their host oyster.  South Sea pearls come from the ‘Pinctada Maxima’ oyster – also known as the Silver-lipped or Gold-lipped oyster.  The quality of the mother of pearl inside of these shells will dictate the quality of the nacre and the color of the pearl that will come from within that oyster.  South Sea pearls come in a range of warm and romantic colors.  Bright Whites, warm and charming golden hues and sophisticated silver pearls are typical of the South Seas. Freshwater pearls are available in virtually any color.

Freshwater pearls that are known from a source area may typically form in specific colors such as pinks, or whites, or with a strong overtone or orient.

Commonly though, freshwater pearls will be treated to unify color.  Dying, pinking, bleaching and irradiating are the most common color treatments in pearls.  These treatments make many more colors possible and available to a larger market.

Most treatments are stable, however dyed pearls may sometimes stain the silk they are strung on.  This is a good indication of treatment.

 

Size

The size of a pearl can range from type to type.  Generally speaking, pearls can come anywhere between 4mm and 22mm.  This of course, is dependent on what type of pearl you are looking at.

Freshwater pearls have the largest size range – anywhere from 4mm to 11mm.  Akoya pearls have the smallest range of sizes, most commonly occurring between 6 and 7.5mm, although the can range between 5.5mm-8mm.  The 8mm range for an Akoya pearl is substantial price jump and they do not frequently occur this large.

Tahitian and South Sea pearls are known for their size.  Tahitian pearls are available between 8mm and 14mm while south sea pearls range from 10mm to 13mm.  Obviously larger pearls are available however they are not the norm.

One of the main reasoning’s for substantial size difference is water temperature and host oyster size.  Obviously the larger the oyster is the increased chances of producing a bigger pearl.  Also, the warmer the water is, the faster the metabolic rate of the oyster thus secreting nacre (what the pearl is made of) at a quicker rate.  South Sea and Tahitian pearls are warm water, and Akoya pearls are cold water.

 

Shape

Pearl shape is one of the 7 value factors contributing to the overall value of a pearl.  There are 7 basic shapes that the value system follows.

• Round
• Near Round
• Oval
• Button
• Drop
• Semi-Baroque
• Baroque

Working down from the top of the list, pearls go from symmetrical to irregularly shaped.  There also may be variations in the pearl such as noticeable rings that are evident by eye and touch. These pearls would be referred to as ‘circled’ or ‘ringed’ pearls.

Quite commonly pearls will take the shape of the bead nucleus that is inserted into the oyster or mussel.  The irritant initiates the secretion of nacre which then forms in concentric layers around the nucleus (or any intruder working its way into the mollusk).  The pearl, in turn, will most likely become a softer, larger shape of what’s inside.

 

Nacre Quality

Nacre quality is determined by the thickness of the nacre.  Obviously the thicker the nacre the larger, more durable and lustrous your pearl.  Pearls with thin nacre can appear chalky and dull and are more easily susceptible to damage.  Nacre quality will often be summed up as Acceptable or Not Acceptable.

 

Matching 

The last value factor when grading pearls is Matching.  (if applicable)  Some pearls may be individual in which case this value factor would not be graded.

Earrings, strands and other pieces that use more than one pearl would be valued on how accurately and precisely the pearls are matched.  The matching is valued based on using the other 6 value factors and how unified the grouping of pearls is overall.  Pearls that share similar grades for other factors in determining overall quality will rank higher on the matching scale than pearls that are matched in suites with varying colors, size, surface quality etc. unless of course the variance in size and color is intentional.