Their wearability is undisputed. They effortlessly accent a pair of jeans and white cotton shirt, while perfectly complementing a gown for the big occasion. They say understated yet feminine when worn by the political A-listers Michelle Obama and Kamala Harris; they say fun and individual when worn by Harry Styles; they say chic yet serious when worn by CEOs Carol Tomé and Julie Sweet.

The spirit of Coco Chanel – who wore ropes of cultured pearls as well as fake ones – lives on. And let’s not forget Elizabeth Taylor who, after a long line of Spanish kings, owned the stunning and record-breaking La Peregrina.

La Peregrina: A natural pearl, diamond, ruby and cultured pearl necklace, by Cartier, from the collection of Elizabeth Taylor. The necklace sold for nearly $12m in 2011 © John Muggenborg/Alamy

But what should we know when looking at pearls for ourselves?

Let’s start at the beginning, with natural pearls and cultured pearls. Today, natural pearls are rare. Step back to just over a century ago and the seminal The Book of the Pearl: The History, Art, Science, and Industry of the Queen of Gems, by George Frederick Kunz and Charles Hugh Stevenson (1908), barely gives cultured pearls the time of day, such was their infancy.

Over-harvesting of the world’s natural oyster beds as well as changing economic demands – e.g., the Gulf was once a big supplier of natural pearls until another industry, oil, took over its seas and human resource – meant that by the mid-20th century natural pearls faced the end of their natural commercial life.

Pearls are produced by either bivalve molluscs or single-shell gastropods when an irritant enters the shell either naturally or by human intervention. This irritant promotes the growth of nacre which coats the irritant to form the pearl. Nacre is made up of the mineral aragonite and the insoluble protein conchiolin.

Although natural pearls are rare there are fine examples to be found in antique settings; cultured pearls remain abundant, and they range hugely in quality – and price. Both natural and cultured are found in saltwater and freshwater.

 Art Deco natural saltwater pearls combined beautifully with diamonds, in our Pearl Edit.Click here to view the Pearl Edit

A pearl’s colour originates in the type of oyster used to produce it. The main saltwater species are:

Pinctada margaritifera, a black-lip pearl oyster, which has a wide geographical spread and seven varieties. P. margaritifera cumingii produces the Tahitian pearl with its dark, grey-to-black nacre, and overtones of blue, green, purple and pink.

Pinctada maxima is responsible for the South Sea pearl. P. maxima is the largest pearl oyster to be found, which in turn produces some of the largest cultured pearls, between 8mm and 20mm. There are two varieties, the gold-lipped and the silver-lipped, which give the South Sea pearls their warmer shades, and silver and gold hues. The larger size – and thicker nacre – come from being grown in warmer waters, and there's an increased probability of a baroque pearl forming. Baroques are non-spherical pearls, which many contemporary designers are exploiting to the full to make lively, unique pieces.

 Contemporary designers, such as Julia Lloyd George, here, are using baroque pearls to great effect.Click here to view the Pearl Edit

Pinctada fucata – or the Akoya pearl oyster – could be said to be the pearl oyster which kicked off the cultured pearl industry. This is a smaller species, but it is the one chosen by Kokichi Mikimoto in the late 19th-century with which to develop his cultured pearl business. Mikimoto was granted a patent in 1896 for the process he developed. Akoya pearls have stood the test of time, and so too has Mikimoto, which to this day remains one of the leading jewellery companies in this field. Akoya pearls have a white body, though they can also be found in shades of pink, silver, blue and yellow. Their diameter is 6-8mm, and they have a bright lustre. They are the classic spherical pearl, and are produced throughout Japan and China.

Two other notable types of pearl are the Fiji black pearls and the Cortez. The Fijian has an extraordinary range of hues and comes from the comparative newcomer J. Hunter Pearls, which harvested its first crop of Fiji pearls in 2003. Only about 25,000 pearls are harvested each year. The pearl oyster at the heart of the operation is P. margaritifera typica. The Cortez pearl hails from the Sea of Cortez, in Mexico, and is produced by the Pteria sterna or rainbow-lipped pearl oyster. Like the Fijian, harvesting is limited, which makes both pearl types relatively rare, with the ability to fetch premium prices.

Freshwater pearls are cultured using mussels rather than oysters. They are mantle-tissue cultivated rather than bead cultivated, which increases the tendency to throw baroque or non-spherical pearls. China dominates production, and they are the most common pearls on the market.

There are several words that crop up again and again when assessing pearls. The GIA (the Gemological Institute of America) has seven value-factors: size, shape, colour, lustre, surface, nacre and matching. As non-professionals, however, what can we look for? Like any gem, the pearl should speak to you. Do you want a perfect sphere or an irregular “baroque” pearl? Are you looking for a dramatic peacock hue, a creamy softness, or are you wanting to be pretty in pink? Do you want the “satiny” finish of Tahitian or South Sea pearl? And what, actually, is lustre? Answer: It’s the amount of light returning from the surface of the pearl as well as the sharpness of reflection. Look for excellence in both.

You may also come across Keshi, Mabe, and Conch pearls from gastropods. Keshi pearls are all nacre and no nucleus, with a flattened look reminiscent of a certain famous breakfast cereal. Each one is unique. They’re fun and idiosyncratic; produced often accidentally, as a by-product of the cultured pearl industry. A Mabe is a large half-pearl – a blister pearl – which when removed from the interior of the host’s shell is hollow. This chamber is filled with resin and backed by mother-of-pearl. They are perfect for pendants, or any piece of jewellery which needs a flat back. Though the term Conch Pearl is much used, they are not true pearls. They have no nacre. These gorgeous pink gems are, however, wonderful jewels and can be found in some of the best pieces of jewellery from the leading houses, such as Harry Winston and Tiffany & Co.

Any budding pearl collector should be aware that pearls can lose their lustre. Looked after properly, however, they will retain their beauty for generations. They can be affected by acidity, so take care if you wear your pearls frequently. Apply hair spray and/or perfume before you put on your pearls. Wipe your pearls carefully after wearing – with silk, preferably – to remove any residues they may have picked up. And don’t store them in cotton wool. This can draw the moisture out of them, eventually leading to cracks. Again, a silk cloth makes the perfect purse to keep your precious pearls lustrous and long-lived.

Banner Image: Tahitian black pearl in a black-lip oyster shell. © Rafael Ben-Ari/Adobe Stock