Pearl Education

Natural Pearls Defined

Natural pearls are calcium carbonate secretions which form within mollusks without human intervention.



Natural Pearls - Accidents of Nature

Natural pearls are formed randomly and really are simple accidents of nature. When a certain type of irritant, such as a parasite, becomes lodged in the tissue of a mollusk, the animal responds by secreting a calcium carbonate substance called nacre to coat the intruder and protect the mollusk. Over a period of several...

Measuring Pearl Quality
Pearl quality and thus, the value of a pearl is measured according to a combination of several varied factors are: the type of pearl, the thickness of its nacre, its luster, the cleanliness and texture of its surface, its shape, its color, and its size.


Because the pearl is a naturally occurring organic gemstone, created by living creatures, these factors can and do vary widely. Although all of them affect the ultimate value of a given pearl, some of the factors are...

Pearl Nucleus Defined
A pearl nucleus is a bead or other object implanted into the gonad of a marine mollusk or into an existing pearl sac in the gonad or mantle of a freshwater mussel around which nacre deposition occurs.

The Pearl Nucleus and Nucleation/Grafting
Pearl farms vary depending on the type of mollusks being produced. But the one thing all pearl farms share is the process of nucleating the mollusks to produce a pearl. Every cultured pearl produced commercially today, except for...

Pearl-Producing Mollusks (Pearl-Producing Bivalves)
Mollusks represent one of the world's earliest forms of animal life, and date back over 550 million years. Actual pearl-producing mollusks first appeared 530 million years ago, when mollusks developed shells. The scientific discoveries of pearl producing mollusks illustrate the intrinsic and irrefutable value of the world's most historically treasured organic gem.

(A fossilized shell of an Abalone from Baja California, Mexico, photo...

Pearl Size Is Measured in Millimeters

A pearl's size is measured according to its diameter in millimeters. Sizes range from 1 millimeter or less, in the case of very tiny pearls, to as much as 20 millimeters (more than 3/4") for large South Sea pearls.

The Average Pearl Size Today is 7.0-8.0 Millimeters

Most white pearl strands sold today fall in the 7.0 to 8.0 millimeter range. This is considered a classic, conservative size.


A 6 mm and a 12 mm pearl

The Larger the Pearl Size, the...

Pearl Shapes Vary Widely
Because pearls are natural organic gems created by a myriad of living organisms, they occur in a wide variety of shapes, many of which are quite unique and interesting. Also, cultured pearls tend to be rounder than natural pearls because (saltwater) cultured pearls usually have a bead inside that will help guide the shape.

Some shapes are distinctively unique to certain species of mollusks, as is the case in Abalones (Haliotis spp) that commonly produce conical or...