Grading

There are several systems of Pearl Grading. We use a simple version of our own blend of several systems to make it easier to understand the grades used in our communication and in our catalogue:

 

Skin Surface

Lustre

Lustre is essentially how and to what extent a pearl reflects light, from the surface or just under the surface of the pearl. Lustre is graded into: Poor or Low, Medium, High, Excellent and Gem.

 

Orient and 'Life'

By definition, the orient is an optical phenomena that produces iridescent colours on the surface of pearls. It is caused by interference and diffraction of light from within the surface of the pearl. Technically speaking, any of 'reflection', 'refraction', or 'diffraction', can create 'orient'. 

Thus the 'life' of the skin will vary between pearls. Mostly, if the nacre of the pearl is thin, then the pearl is likely to have low orient and lower 'life'. This quality is both visual and sentient. There can be pearls that look great with medium lustre but have a lot of 'life'; they don't have to be top lustre to have a lot of life.

Markings

A Grade - Where marking and blemishes on the pearl surface covers a very small area. The skin is 90% plus 'clean' or smooth.

B Grade - Where the pearl surface is 2/3 clean - i.e. one side faces up clean, where surface marks or blemishes are not visible.

C Grade - Where the surface of the pearl is 2/3 'un-clean' - where there is no clean face.

Marks or blemishes will always be visible.

D Grade - This is a low quality pearl. Most of the surface has blemishes.

E Grade - Rejection - the skin is of such low quality that it is not regarded as commercially acceptable. In some cases the nucleus is exposed. 

 

For a full and detailed knowledge base please click on the link to the CIBJO "PEARL BOOK", which covers: terminology, categories, classifications, care, production, genealogy, and many other topics.

Colours

White and Gold South Seas: Species: Pinctada Maxima:

These are produced from White lipped, Silver lipped and Gold lipped Oysters, found in Australia, Indonesia, Philippines, Myanmar (Burma), as being the major global producers. There are numerous colours available from White, Grey, Silver, Creme's, light Gold to darker Golds, and even 'Blues' - which are part of the dark grey spectrum; and all the shades of colour in between.

Tahitian: Species: Pinctada Margaritifera:

Tahiti or French Polynesia and also the Cook Islands of New Zealand are the major areas where these oysters are farmed, however, there are several other areas around the world where these Black lipped oysters are found. 

 

Pearls from the Pinctada Margaritifera can range in colour from very light grey, even off white, bronzes, yellows, greens, peacock green, aubergine, all shades of grey, gunmetal, blues, as some of the spectacular colours.

Shapes of South Sea and Tahitian Pearls:

Shapes determine the value of pearls.​

Rounds

The most prized and valuable pearls are perfectly round, and these make up only a small percentage of all the shapes produced. Then there are various levels of roundness, from 'Round', which is virtually perfectly round with hardly any variance; 'Near Round' which is round looking but not completely round; to 'Off Round' to 'Semi Round'. The latter are used mainly in pearl stud earrings, or stranding, and appear round or 'roundish'.​

Ovals, Egg shapes and Drops

These are next most sought after by value, but please note that people have different tastes in fashion; some people prefer certain shapes even although they may have a commercially lower value. For example, some people may prefer baroque or circle over the classic round shape. Pearls are personal and individual, beyond their values and grades.​

Baroque

Baroque are misshapen pearls resulting from infection around the nucleus during the cultivation process. The Oyster in self-defence, has secreted nacre covering the infection, to give rise the random shape. Often, when these pearls are drilled, a rotten organic matter will drain from the pearl with a terrible stench, which then has to be cleaned for the smell to dissipate. Baroque Pearls have unique characters and make stunning necklaces and individual pieces of jewellery.​

Keshi

Keshi is a by-product of the culturing process, where the oyster rejects the nucleus or bead in the cultivation process. When the pearl is removed from the oyster, the nucleus or bead is found next to the pearl. There are some exquisite shapes with Keshi, but to be absolutely sure these pearls are genuinely Keshi and not baroque, these pearls should be X Rayed. They also may contain organic matter, which needs to be drained if the pearl is drilled.​

Button

Buttons are like 'squashed' pearls. They are opposite to ovals. With Ovals the axis of the pearl is along the length or long axis of the pearl. With Buttons, the axis is along the shortest length of the pearl. Buttons Pearls are ideal for earrings, where the pearl lies flatter on the ear. There are several types of buttons: from flat to high dome, to virtually round, to flat on one side and domed the other side, as some examples.​

Circle

Circle pearls have different levels of 'grooves' or 'rings'. Some example have only one or two grooves, while some have lots of rings. Circle pearls can be roundish, drops, buttons and oval shaped.

Triangle or "Tringle"

Triangular pearls are unusual: they are shaped like a triangle with a flat 'bottom', and 'flattish' sides. They would be closest in shape to flat bottom drops. 

Sizes

The larger the pearl, they are more rare, and more valuable.

X Ray Images

Following are actual x ray images, showing different shapes of South Sea Pearls. You are able to see the nucleus, various nacre thicknesses, and air spaces in some of the pearls such as baroque. We regularly X Ray any new stock to check the nacre thicknesses, as an additional quality test, and to maintain a high standard of quality and quality control.

Pearl Treatment

After pearls are farmed there is what is called "polishing to 'Traditional Standards'". This is

Essentially a 'clean up' only, and is usually not declared nor needed to be declared by either

Australian, or international standards.

 

There are several other treatments, some which are chemical, such as bleaching, dying and coating that can be done by changing the colour of the pearl or the outer appearance of the pearl to improve the appearance of the skins.

The onus is on the Company doing the treatments and the final seller to divulge any treatment(s), and then down line to the final customer; also in accordance with the commercial laws and trade practices of the countries where they are sold.

© 2019 by Diman Co Jewellers Pty Ltd