Pearl buying guide by J K Diamonds Institute

Pearl is generally valued based on their origin, formation and quality factors.

The three questions commonly asked by customers are

1) Difference between Natural and Cultured Pearl

2) What are Fresh water and Saltwater Pearl?

3) Whether treated or not?

The following blog is guidelines for buying Pearl.

Natural Pearl

They are formed accidentally and are rare to find.

When foreign objects such as worms, snails, crabs, fishes, tiny pieces of fish bones or tiny stones like pebbles, sand, etc. penetrate into the space between shell and mantle tissue, where they are trapped. To protect itself the mollusc secretes nacre to ease the irritant. This is a long process that finally forms pearl on the shell wall.

Another method of Natural pearl formation is when the foreign object tries to enter the oyster. The oyster creates depression in the mantle in which the irritant is trapped and forms a sac of mantle tissue (Nacreous layer) on irritant which in turn forms pearl.

Cultured Pearl

Cultured pearls are the ones that generally found in the market today. They are pearls formed due to human interference wherein nucleus is placed in gonad (reproductive part) of the pearl. Cultured pearl can be beaded and non beaded. Bead generally contains shell with mantle tissue of the donor oyster. Hence, like natural pearl, nacre surrounds the bead and forms pearl sac. Famous beaded cultured pearl are Akoya, South Sea and Tahiti.

Non beaded pearl: A small piece of mantle tissue from another mollusk as a donor for forming  pearl sac, it is surgically implanted into the gonad (reproductive organ) of a mollusk.

Freshwater & Saltwater Pearls

These are two types available in the market. The difference is explained below:

 Grown by musselsGrown by oysters
Non NucleatedNucleated
Inserted between mantle and shellInserted in gonad (reproductive organ) part of the oyster
Grown in ponds, rivers, and lakesGrown in sea, oceans.
Softer luster with less shineBrilliant luster with good shine.
Thicker nacreous layer (almost full nacre)Comparatively thinner nacreous layer
 Lake Biwa and Lake Kasumigaura in Japan, China, United States (Mississippi River Basin).Red Sea, the Persian Gulf, and the coastal waters of China, Japan, Thailand, India, Burma, Indonesia, and Philippines in Southeast Asia, as well as Australia and Tahiti in the South Pacific.
Produce 40 to 50  pearls in a mussel at a time1 0r 2 pearl in an oyster at a time
Different colors and different shapesLimited colors and more or less spherical in shape
Growth Period: 2-7 yearsGrowth Period: one year for akoya, 2–4 years for Tahitian and South Sea

The process of nucleus with mantle tissue inserted forms a cultured pearl. Mussel is placed in the net and periodically checked. Once the pearl is ready, it is utilised in jewelry. The images below are of a pearl cultivation farm.

Treated or non treated?

Bleaching: Light coloured as well as white Pearls are bleached to make it more vibrant. Hydrogen peroxide solution is used to bleach the pearls to get desired results. The pearls are placed in the solution for a long period of time which changes the overall colour of the organic pearl. To achieve good colour it takes approximately one week to two months.

Irradiation on Pearl Stone

When light coloured pearls are exposed to gamma rays, the irradiated Pearls will achieve an iridescent bluish or greenish grey colour.  Irradiation is used mainly for fresh water pearl.

Dyeing treatment: Pearls are porous and hence dye or oil can get absorbed giving pearl a beautiful lustre and colour uniformity. Pink pearl is dyed, especially to fufil demand of the the US market.


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