So – how should you choose pearls?

Like diamonds, pearls have a check list, which is a straightforward guide to getting the best value for money.

COLOUR: natural pearls occur in a wide variety of colors. Generally, this will range from cream, to silver-white, to black. Within this, there a million nuances of tone and hue, which is why it can often be so hard to matched pearls. Different varieties of pearl have different qualities of colour. For instance, Akoya cultured pearls are white lustrous pearls with usually cream or rose colored overtones. These are the classic Japanese pearls most often used in pearl strands. Freshwater pearls come naturally in a enourmous range of cream and pink tones. They are also commonly dyed in colours ranging from pastel pinks, peaches and lavenders, to darker mulberry, blue and green.

South Sea cultured pearls come in various shades and lustres of white, often with silver or rose overtones. They are noteably larger in size than the Akoya pearl, and hence tend to cost considerably more. Tahitian pearls come most often in shades of black and grey, which is produced naturally. Their large size and colour is especially desirable, and hence tend to command high prices.

LUSTRE: When marine mollusks sense irritantents within their shells (such as sand, grit, or implanted nuclei, as in a cultured pearl) it begins to secrete layers of semi-opaque calcium carbonate called nacre to coat the irritant, and thus protect itself. Nacre build up in concentric layers over time and thus, the thicker the nacre, the more lustrous the appearance of the pearl. Lustre is the term given to the reflective quality of the pearls surface and it is this above all other that determines the quality of the pearl. The thickness of nacre is of paramount importance in assessing a pearls quality. Pearls which are farmed cheaply for the mass market often have a very thin nacre layer due to the fact that they have only been left to grow for a short time (ie. a year) allowing only minimal deposit of nacre. Good quality pearls have a minimum nacre thickness of between 0.35 and 0.5mm thick, achieved by allowing between 2 and 3 years for growth and this is reflected in the lustre of the pearl. Freshwater pearls, as they do not have a nucleated center, take longer to grow and may need 4 to 6 years to achieve a good level of nacre. When you buy pearls, always feel free to ask the company or salesperson you are buying from to tell you what the average nacre thickness of their pearls is.

Generally, low-lustre pearls are dim, flat and monochromatic, but a higher grade of pearl with thicker nacre produces a resilient pearl with far few surface blemishes. This creates a sharp, high-contrast surface that is almost mirror-like in its reflective qualities.

SIZE: Yup – size matters; and in the case of the pearl too refers to the diameter which is measured in milimetres. Regardless of variety, the larger a pearl is the more rare, and thus, the more valuable. Large pearls can be created in a variety of ways.

Firstly large molluscs, or certain species create larger pearls by very merit of their size or genus. Secondly large cultured pearls can be created by inserting a larger nucleus than normal. There are obvious risks with this, as the animal may reject a nucleus of a large size, or indeed the size of the nucleus may cause the mollusc to die before a pearl has the opportunity to develop. Large nucleii also affect the complexion of the pearl, as larger, more mature pearls will often have a rougher, less uniform surface. Round pearls are measured according to their diameter, while baroque pearls are measured by their length and width.

Akoya’s tend to measure 6 to 8 millimeters in diameter; 8mm is considered large. Freshwater pearls come in at approxiamtely 5 to 6.5 millimeters, for the best quality. South Sea and Tahitians are amongst the largest pearls, often measuring between 11 and 13 millimeters - large by any pearl standard. The relatively large size of Tahitians and their wonderful array of colours is a contributing factor to their high cost. Tahitian and South Sea pearls can be found in varying shades of black, grey, pink, and gold amongst others. A good round Tahitian with excellent lustre will fetch a very high price, but some good Tahitians can be found in baroque or off round shapes for less (although they are still comparatively pricey).

SURFACE QUALITY: The term refers to the types and amount of blemishes or marks on a pearl. Most natural pearls have some blemishes, and importantly it is this which separate them from imitation pearls, and makes them easier to identify. Clearly unacceptable blemishes include holes, pitts or cracks in the surface, and flaking nacre. The cleaner the pearl, the higher it's value.

SHAPE: In the minds eye, a classic pearl is one which is uniformly round and even. Unfortunately completely round pearls are the rarest of pearls, and in consequence the most expensive. However for very reasonable sums of money, pearls can be purchased which appear round to eye, but are in fact slightly off round making them cheaper. Pearls can also be bought in oval, flat button, discoid, and baroque (irregular) shapes, and these all have a charm of their own, which may suit your style better than the traditional classic round pearl.

Whatever your preference, just take care when buying and enjoy when wearing.

By Vanessa Frisbee