Buying Guide

Grading the Qualities of Pearls

Qualities of Pearls

A pearl is a unique, organic gem created in a living mollusc. One pearl may vary significantly from another in its origins, characteristics and treatments.

These qualities may suit a particular style of jewellery and budget but, without a careful and consistent approach to grading, buying pearls may be confusing.

The most widely accepted system of grading worldwide for natural and cultured pearls is the Gemological Institute of America's Pearl Description System.

Qualities of Pearls - Pearl Grading

There are 7 different quality factors in the GIA system that we use to describe and determine the beauty of a pearl, including:

  • Size
  • Shape
  • Colour
  • Lustre or Luster
  • Surface
  • Nacre Quality
  • Matching

Read our guide below to learn more about the 7 different value factors that are used to describe and determine the beauty of a pearl. If you would like to know about our commitment to quality, read more about Our Standards.

Size

Qualities of Pearls - Size

A round pearl is measured across its diameter in millimetres.

For non-spherical, baroque and other shapes of pearls, both the length and width of the pearl is measured.

The most popular Akoya and Freshwater pearl sizes for earrings and necklaces are between 7 and 9mm in diameter.

South Sea and Tahitian pearls are typically worn between 9 and 11mm in diameter, or larger for more statement pieces.

Shape

Qualities of Pearls - Shape

Pearls have a variety of shapes, with the classic round and drop shapes being the most popular to wear.

The different qualities of a pearl's Shape in the GIA Pearl Description System are:

ShapeDescription
Round Uniformly spherical
Near-round Almost spherical, with some minor variations
Oval Symmetrical, rounded and oblong
Button Symmetrical, slightly flattened
Drop Symmetrical, pear shaped
Semi-baroque Irregular, not quite symmetrical
Baroque A pearl with an irregular shape

Akoya pearls tend to be most consistently round, although other nucleated saltwater pearls and increasingly Freshwater varieties can also be found in round shapes. Baroque shapes can be particularly individual and fun to wear.

Colour

Qualities of Pearls - Colour

One of the most unique qualities of a pearl is its colour.

At Winterson we grade the colour of the pearls in our jewellery with the GIA Pearl Description System. The table shows the different Colour characteristics that may be displayed by a pearl.

CharacteristicDescription
Bodycolour The dominant, overall colour of a pearl
Overtone Some pearls may display one or more additional overtones of colour in the reflection near the top of the pearl
Orient The rainbow colours that are displayed just below the surface of a pearl, usually those of a baroque shape, as it is rotated

The main bodycolour of a pearl will be described, with a note also being made if the pearl has an overtone colour or an iridescent rainbow effect. We will always disclose whether a pearl has been treated for colour.

Lustre

Qualities of Pearls - Lustre

Lustre, or luster, describes the intensity and sharpness of light reflected from the surface of the pearl. The different qualities of Lustre in the GIA Pearl Description System are:

LustreReflections of Light
Excellent Bright and sharp
Very Good Bright and near sharp
Good Bright, but not sharp, slightly hazy
Fair Weak and blurred
Poor Dim and diffused

Of all a pearl's qualities, lustre is perhaps the most important to consider.

The Surface of a Pearl

Qualities of Pearls - Surface

Most pearls will have some normal surface characteristics or irregularities. The surface condition of a pearl is judged by the size, number, location, visibility and types of these blemishes.

The different qualities of Surface in the GIA Pearl Description System are:

SurfaceDescription
Clean Blemish free, minute surface marking
Lightly Spotted Some minor surface irregularities
Moderately Spotted Noticeable surface characteristics
Heavily Spotted Obvious, possibly affecting durability
Poor Dim and diffused

The presence of these surface characteristics may add to a pearl's individual beauty but, if significant, could suggest that its durability might be affected.

Nacre Quality

Qualities of Pearls - Nacre Quality

Nacre is the unique layered material that gives a pearl its reflective and iridescent properties.

A pearl's beauty and value will be influenced by the thickness and crystal structure of its nacre.

The table describes the different types of Nacre Quality that are possible.

NacreDescription
Acceptable No noticeable nucleus, not chalky
Nucleus Visible Thin nacre, with poor pearl durability
Chalky Dull appearance, with poor lustre

All our pearls are selected for having the highest grading of nacre quality, which is described as Acceptable under the GIA's Pearl Description System.

Matching

Qualities of Pearls - Matching

Matching describes the uniformity of appearance of two or more pearls that have been used in jewellery, for example in necklaces, bracelets or earrings.

The consistency of the other six Qualities should be considered.

MatchingDescription
Excellent Pearls are uniform in appearance and drilled centrally
Very Good Some minor variations in uniformity
Good Minor variations in uniformity
Fair Noticeable variations in uniformity
Poor Very noticeable variations in uniformity