Pearls - Akoya & Freshwater 

Pearls are regarded as one of the five precious gemstones of old alongside ruby, sapphire, emerald and diamond.  They are treasured for their iridescent lustre known solely to pearls as ‘orient’.  Their orient is a reflection of the quality of the ‘nacre’ or ‘mother of pearl’ coating seen on the outside of the pearl, hence the higher the quality of the nacre means the higher quality of the orient and the pearl itself.   Today naturally occurring pearls are exceedingly rare and only account for a tiny fraction of worldwide pearl sales. 

The overwhelming majority of pearls in the market today are known collectively as cultured pearls.  Cultured pearls are still grown in certain species of oysters or mussels like their natural counterparts. However, man has intervened and initiated the growth of the pearl instead of nature.   The most common and the most affordable of the cultured pearls are the freshwater pearls grown by mussels in freshwater rivers, lakes and dams with China being the predominant producer.  Freshwater pearls can be typically grown in perfectly round sizes of up around 11mm with larger sizes predicted to be commercially available in the future.

Mohs’ Hardness: 2.5-4.5
Specific Gravity: 2.12-2.2.78
Refractive Index: 1.530-1.690
Birefringence: 0.156
Optic Sign & Character: Isotropic
ICA Code: N, C and or T
Treatments: May be bleached and or dyed
Incidence:     Common (freshwater and Akoya)
    Rarely (south sea)
Purpose: To Improve colour
Durability: Fair
Special Care: Sensitive to chemicals
Synthetics: Cultured
Possible Imitations: Shell based pearls and other coated glass or plastic beads

South Sea Pearls

The largest, finest and most valuable cultured pearl in the market today is the South Sea Pearl.  Unlike both the Akoya and freshwater cultured pearls, the South Sea Pearl is in a class all of its own as it is generally grown with an exceptional orient in sizes larger than 10mm round and growing up to and over a massive 20mm round.   Cultured South Sea Pearls are grown in the tropical waters of the southern hemisphere and can be broken down into three man groups; white, black and golden South Sea Pearls.  Some well-known farming locations for these different varieties of South Sea Pearls include; Northern Australia, Tahiti, Indonesia, The Philippines, Myanmar (Burma).  
Only a small proportion of South Sea Pearl oysters that are nucleated will go onto produce a fine quality South Sea Pearl.  Much depends upon the whims of mother nature.  Many of the oysters do not survive the surgical nucleating operation.  Others are weak and susceptible to disease.  Then there are storms, attacks of predators and parasites, or a lack of sufficient nutrition in the water.  All these factors result in either poor quality pearls or pearls that are too imperfect to be used.   A perfect pearl is a rare event, blessed by nature and highly valued.
oagems.com has an ever changing range of excellent Tahitian South Sea Pearls at all times


Grading and pricing of South Sea Pearls can seem complicated because there are multiple factors to consider i.e. shape. lustre and surface.  
Grading codes.
SHAPE
R1    Round
R2    Near Round
R3    Semi Round
DR1    Smooth drop
DR2    Bell shaped,  small circle near top or slight circle
DR3    Triangle, knob on the top or slightly asymmetrical shape

LUSTRE
AAA    Very good lustre
AA    Good lustre
A    Fair Lustre
-A    Poor Lustre
SURFACE
AAA    Spots on  10% or less of the surface
AA    Spots on 30% or less of the surface
A    Small spots on more than 30% of the surface
-A    Large spots on more than 30% of the surface
Mohs’ Hardness: 2.5-4.5
Specific Gravity: 2.12-2.2.78
Refractive Index: 1.530-1.690
ICA Code: N, C and or T