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Gemstone Guides


your guide to pearls

Your guide to pearls

The World is Your Oyster 

AnchorCert Gem Lab offers pearl identification reports.

The laboratory identifies:  

  • Natural Pearls
  • Beaded, cultured pearls
  • Non-beaded cultured pearls
  • Imitations 

Strings of pearls and loose single pearls can be examined and, depending on client requirement, results can be provided as written AnchorCert Reports or verbal consultations.

The choice of pearl jewellery, both in terms of design and in relation to the type, size and colour of pearls employed, has never been greater but keeping up with the latest developments can be tricky. 
The culturing of pearls is a constantly evolving process. The Japanese made a huge turn in the wheel of evolution when they perfected the process in the early 20th century but in the last 15-20 years the Chinese have taken over their mantle and moved it on again and we are now seeing pearls in sizes, shapes and qualities that simply didn't exist twenty years ago.
One of the main developments has been in the production of freshwater pearls, which were traditionally considered inferior to their saltwater cousins. Freshwater pearls used to be small and shaped like rice crispies – but now thanks to new techniques and the hybridization of mussel varieties to create bigger types – they can be up to 16mm in size and perfectly round, so to the untutored eye it can be difficult to distinguish them from the larger South Sea varieties and this is undoubtedly having an impact on the market.
All cultured pearls are created by introducing either a solid bead and mantle tissue, or just some tissue into the oyster or mussel. The creature then coats this with layers of ‘nacre’ – a substance which occurs naturally inside its shell, to create a pearl. This process happens naturally in the wild and prior to pearl farming, was responsible for the creation of the now increasingly rare natural pearl. Generally speaking, the thicker the layer of nacre the greater the luster of the pearl and the more its value.


Once upon a time pearls were small and creamy or pinky white, now coloured pearls are all the rage. So where do these new colours come from? The answer is different types of oyster or mussel. The ‘black lip’ oysters of Tahiti and the Cook Islands give deep black/green, aubergine and pewter shades, while the ‘Gold Lip’ and ‘White Lip’ oysters give, as their names suggest, more golden or silvery pearls. South Sea pearls – the most valuable of all – tend to be silver/white to creamy champagne and gold. While Akoya (the original cultured pearl) tend to be white/pink/cream to silver grey. Freshwater pearls are generally white but can naturally be pink, peach, lavender or salmon.

However, not all pearl colours are natural. At the cheaper end of the market some pearls are dyed or stained to produce different colours and the use of silver nitrate and other techniques to produce greys and blacks is common practice. Some pearls are also being irradiated or heated to create darker fancy pearls but it is too early days to know what the long term effects of this are likely to be.

Types of Cultured Pearl


A beaded cultured pearl produced in the Akoya pearl oyster from Japan. Sizes are relatively small at 2 – 10mm, and colours tend to be pale – cream, white/pink and silver.
SOUTH SEA  Cultured pearl from the silver or golden lipped oyster. Cultured in areas of the Indian and Pacific ocean, including Northern Australia, Indonesia and the Philippines. Sizes are 10 – 22 mm and colours range from silvery white and cream to champagne and gold.
TAHITIAN Tahitian pearls are naturally coloured resulting from grafting and breeding in a natural environment, the French Polynesia. Sizes are 8 – 18 mm.
FRESHWATER These generally nucleus free cultured pearls produced in mussels and are mainly from China. They come in many different shapes and sizes and in colours from white, peaches, pinks and lavender. Sizes are 2-16mm or larger depending on the variety.
KESHI A non-beaded pearl that is formed accidently or intentionally in marine pearl oysters such as the Akoya oyster. Keshis are a byproduct of the culturing process. Keshis are often large, free-formed shaped pearls which are said to resemble flower petals measuring up to 25mm or more. Colours tend to be dependent on the mollusk they form from.


Pearl Quality: The quality of a pearl depends on five criteria:



The quality and quantity of light a pearl reflects from its surface or near surface. A good pearl should be deeply lustrous – the thicker the coating of nacre the better the luster will be.
TEXTURE Good pearls should ideally be flawless without any blemishes or dents.
SHAPES Pearls can be many different shapes but the most common are button, drop, round, oval and baroque (or irregular). Shape does not influence quality. 
SIZE The size of a pearl is measured in millimeters and tends to depend upon the size of the original nucleus and the time the pearl has had to develop. 
COLOUR Colour is a matter of fashion and personal choice. Deeper colours especially browns and greens are currently popular.

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