The AUTORE Five S’s™ South Sea Pearl Classification

AUTORE MODA was founded by Ruby Autore, daughter of Rosario, a pioneer in the pearling industry, and mother Jane, award-winning jewellery designer. The AUTORE Group, founded by Rosario in 1991 is one of the largest South Sea pearl companies in the world. The AUTORE Group, is one of the largest vertically integrated South Sea pearling operations in the world, with control over the full supply chain from sustainable production all the way to a finished piece of Jewellery.
In 2007, The AUTORE Group developed the world's first comprehensive South Sea Pearl Classification Guide as a tool for the trade and consumer alike to identify the five qualities of South Sea pearls, AUTORE Five S’s – Shine, Surface, Shade, Shape and Size™.

AUTORE Five S’s™

The guide considers the quality of a South Sea Pearl based on its ShineSurfaceShadeShape and Size, and provides an in-depth explanation to understand pearl classification.



A South Sea pearls shine comes from its lustre. Lustre is the result of light reflected form the pearl's surface combined with its deep inner glow (iridescence). South Sea pearls are made up of many fine layers of a crystal-like substance called nacre, comprising of organic and inorganic materials secreted from within the living tissue of the oyster. The quality and thickness of nacre gives a pearl both its radiance and its deep glow. The combination of light reflecting on the pearl’s surface and light refracting between each layer of nacre within the pearl is what makes this gem unique. Lustre has the magic to minimise other imperfections and is considered the soul of the pearl.


There are five broad categories of lustre:

I - Brilliant lustre: producing a mirror reflection

II - Excellent lustre: producing a very clear reflection

III - Good lustre: producing a good reflection

IV - Average lustre: the reflection appears opaque

V - Poor lustre: producing very little reflection



The surface of a pearl is essentially its skin. When assessing the surface of a pearl, you mut consider the blemishes and the pearl's grain.


The layers of lustrous nacre is built up over time making it extremely rare to have a flawless surface. As pearls are a gift of nature from a living organism, the most beautiful and valuable pearls may still have slight imperfections. These naturally bestowed 'beauty marks' characteries each pearl as an individual creation. Blemishes come in many varieties, the most common being:

1. Spot: the most common type of blemish, which usually appears as a small, shallow hole, a sunken area or a small indented scar on the pearl's surface

2. Bump: a blemish resembling a raised scar or blister. Bumps are uneven and sometimes discoloured areas of the pearl's surface

3. Chip: an area of the pearl's surface which appears to be cut out of chipped off

4. Scratch: a mark resembling a line produced by scratching

5. Wrinkle: small creases on the pearl's outer layer producing a crumpled or shrunken appearance

A grading system has been developed by AUTORE to identify the extent of visible blemishes, regardless of type.

A. Blemish free or very small blemishes hardly discernable by the naked eye

B1. One to four visible blemishes concentrated on one small area of the pearl

B2. Blemishes visible on 30% of the pearl’s surface, not necessarily on the same area

C1. Blemishes visible on 50% or more of the pearl’s surface, not necessarily in the same area

C2. Heavy blemishes on the majority of the pearl’s surface

D. Heavy or deep blemishes and/or thin coating of nacre

The grading of a Baroque pearl differs from all other South Sea pearl shapes. Its grade is based predominantly on its shape, surface appearance and its ability to be diversely used in jewellery and strands, rather than by reference to its surface blemishes and pearl grain.

A. Smooth skin with good lustre however not necessarily spotless

B. Smooth skin with good lustre, spotted or wrinkled on less than 30% of the pearl’s surface

C. Extremely asymmetrical, spotted or wrinkled on less than 30% of the pearl’s surface

D. A ‘D’ grade baroque pearl could be classified on the following characteristics:

Heavy spotting on the majority of the pearl’s surface

Heavy wrinkling on the majority of the pearl’s surface

Discoloration under the pearl’s surface

Pearl Grain

The pearl grain refers to the composition of the pearl’s skin and its structure. The tighter the structure of the pearl, the less evident is its grain. The grain will appear as slight ripples on the pearl’s surface.

CL (CLEAR) - No pearl grain visible

VSL (VERY SLIGHT) - Very slight pearl grain visible

SL (SLIGHT) - Slight pearl grain visible on 30% of the pearl’s surface

MD (MEDIUM) - Medium pearl grain visible on 50% or more of the pearl’s surface

HY (HEAVY) - Heavy pearl grain visible on entire pearl surface



The species of oyster and the environment in which they grow are the main factors behind determining a pearl’s colour and complexion. Pearls from the Pinctada maxima oyster come in shades of White, Ivory, Silver, Blue, Yellow and rich Gold. Pearls from the Pinctada margaritifera oyster (referred to as Tahitian or Black pearls) come in shades of Aubergine, Blue, Green and Grey, all with various hues.

Colour depth/variations

All of the base colours come in dark and light forms. Some South Sea pearls may be labeled as ‘intense’ when their colour is extremely deep or ‘light’ when there is a soft hint of colour.

Colour code:

I= Intense
L= Light


Variations of these base colours occur quite often and in some cases two colours can be combined. The appropriate description for pearls combining two colours would be I SIL/BLU (Intense Silver Blue) or L YEL/GRN (Light Yellow Green).

White Range

Yellow Range

Black Range



South Sea pearls often show beautiful iridescent overtones, especially pinks and greens. These hues come from the layered structure of nacre and the behaviour of light as it reflects from both the upper and lower layers of the pearl’s surface.





South Sea pearls come in a variety of shapes, making them an incredibly difficult gem to classify without a professionally trained eye. A product of nature, each pearl is individual and unique.


A pearl is considered Round when the variation in its diameter is less than 2.5%.

Near Round

A pearl is classified Near Round rather than Round when the variation in its diameter is roughly more than 2.5%.


The vertical axis of a Drop must always be longer than its horizontal axis. The greater the difference in size between the vertical axis and the horizontal axis, the more unusual and rare the pearl is.


The vertical axis of a Button pearl must always be shorter than its horizontal axis.


Generally speaking, a Baroque pearl is irregular or free form in shape.


A pearl that has one or more parallel grooves etched around its circumference is called a Circle.

Circle category

1 - One to two grooves

2 - Three or more grooves but still good reflection

3 - Multiple grooves distorting reflection

Keshi - Non-Beaded

Possessing an individual allure entirely different to that of a nucleated cultured pearl, a non-beaded South Sea pearl (‘Keshi’) is created by chance when the oyster rejects the nucleus but retains the mantle tissue, that was originally inserted for the creation of the pearl sac. This enables the oyster to continue to secrete nacre which forms the ‘Keshi’ pearl.


South Sea pearls are renowned for their large sizes. The Pinctada maxima oyster is the largest species of oyster capable of producing a pearl. South Sea pearls are measured in millimetres. South Sea pearls commonly range from 9-20+mm, with the majority falling within a range of 10-17mm.

The largest fine quality Round South Sea pearl cultivated by one of AUTORE’s South Sea pearl producers, Cygnet Bay Pearls, measured in at a magnificent 22.8mm.


The weighing unit for pearls is momme, an old Japanese measure of weight still used for all pearls. One momme is equal to 3.75 grams or 18.75 cts.