Pearl Guide

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...

Pearl Surface in Pearl Grading
The surface cleanliness of a cultured or natural pearl has a direct correlation to its value. A pearl can never, according to rules set forth by the FTC, be graded as "flawless", but the degree or percentage of inclusions or surface imperfections can be measured by anyone with experience.

What to Look for on a Pearl's Surface

When grading pearls, the appearance of the surface of a pearl is one of the most important characteristics in determining its overall...

Pearl Treatments Defined
Pearl treatments are defined as any action other than polishing which alters a pearl's appearance which may include:

irradiation
bleaching
heating
filling
waxing
drilling
cutting
faceting and
working

Pearl Treatments just after Harvesting

After harvest, most pearls are always processed in one way or another. This processing may be subtle or less so.
South Seas, Tahitians and Cortez pearls are usually just washed and will undergo minor tumbling with waxed bamboo...

Cultured and Natural Pearl Weight Descriptions

Pearl weight is expressed in carats or grains when describing natural pearls, or kilograms, kan or momme when describing cultured pearls.

When Is Pearl Weight Used Instead of Size?

Most of the time, pearls are described primarily in terms of their size (diameter) and expressed in millimeters. Weight is typically only described within the wholesale trade or when dealing in rare wild pearls such as abalone or conch.

How to Weigh Pearls
Natural...

Grading South Sea and Tahitian Pearls

While there is no internationally recognized number or letter system for pearl grading, there are best-grading practices that are accepted and recognized by all professional pearl dealers within the industry. Understanding grading attributes and quality characteristics of South Sea and Tahitian pearls is imperative to properly shop and compare.

Pearl Grades: Combining Seven Different Value Factors

As pearls have many differing value factors such as...