What determines the price of a pearl

Why two necklaces that look alike are far apart in value.

Two strands of white pearls, laid side by side on the same cloth, can look like twins. One is worth twice the other. The difference lies in six qualities of the single gem and in a seventh, which concerns the way the pearls sit together. Whoever knows how to read them sees the price before learning it.

Time is the first price

A pearl forms in the dark, inside a mollusc, over a span of years. The animal deposits calcium carbonate in minute crystals and, between one layer and the next, a web of conchiolin that holds them together. It repeats the operation thousands of times. Every additional layer is time elapsed, and time is the raw material that is paid for here.

Size

Large sizes remain rare for a physiological reason: a large nucleus strains the mollusc, which more often returns it to the sea. Between a 7 mm pearl and a 9 mm pearl of the same quality the difference in price is sharp, because the growing time changes. Akoya pearls range from 2 to 10 mm, Freshwater pearls reach 20 mm and beyond, South Sea pearls start at 8 mm and reach 16, up to 22 for Australian whites, and Tahitian pearls usually lie between 8 and 13 mm.

Shape

Gemmology recognises seven shapes: round, three-quarter, near-round, drop, button, circled, baroque. The perfect sphere is rare, because the mollusc deposits the material around the nucleus following its own movement, and that movement is seldom regular. In a South Sea harvest most pearls come out oval, drop, circled or baroque: it is in that proportion that the value of a round South Sea pearl lies. Shape weighs on value as much as size, and at times more.

Colour

Colour depends on the mollusc that produced the pearl, and the rarer a hue the more it is worth. Among Akoya pearls, native grey and gold belong to very few specimens. Among South Sea pearls, the hue descends from the inner rim of the shell: silvery lips give the whites, yellowish lips the golds. Among Tahitian pearls, the iridescent green the trade calls peacock comes from Pinctada margaritifera alone.

Lustre

On a pearl of intense lustre the reflection of a window stays small and sharp-edged, and the gem seems lit from within. Where the lustre is weak, that reflection widens and fades. It is the quality the eye recognises first, and the first to move the price.

Surface

A pearl is made of thousands of layers, and almost always carries some surface characteristic: it is the sign of organic matter, grown inside a living mollusc. What counts is the number, the depth and the position. A mark on the side that rests against the skin weighs less than one at the centre of the pearl.

Nacre quality

It is the factor that stays silent to the eye, and it counts for the years to come. Fresh from the water, a pearl with thin nacre and one with generous nacre have the same surface. What tells them apart is time: thin nacre wears away with rubbing, and the nucleus begins to show through. Against the light, through the drill hole, the layers can be told apart; in the laboratory, X-ray measures their thickness while leaving the gem intact. Generous nacre is the reason a necklace remains the same thirty years from now.

The harmony of the matching, and why it weighs most of all

The first six factors concern the single gem. The seventh arises when pearls are brought together, in a strand or in a pair of earrings, and measures how closely they correspond in colour, overtone, orient, shape, size and lustre. To compose a homogeneous strand of large, luminous pearls, thousands of specimens must be selected, and the price takes full account of that work. Two strands of the same size and the same colour can require very different amounts of selection: here the distance between one and the other opens up, and this is the answer to the question with which the page began.

What accompanies the pearl

The value of a MIMÍ creation also includes the work and the guarantees that surround it.

• The selection carried out by the maison at the places of origin: Japan, China, Australia, French Polynesia.
• Three checks on every pearl: at the producer, on receipt in Italy and on the finished jewel.
• The drilling of South Sea and exceptional pearls, carried out in Italy by the maison.
• Hand-knotting on silk thread, pearl after pearl, for Akoya, South Sea and Tahitian strands.
• Mounting entrusted to an Italian workshop with forty years of specialisation, and gold and silver components from RJC-certified Italian suppliers.
• The certificate for the pearl type and the certificate of guarantee; for exceptional pearls, a certificate issued by an international gemmological laboratory.
• The services that accompany the jewel over the years: restringing and hand-knotting, replacement of a single pearl, periodic check.

How to read a MIMÍ product sheet

Every creation states the pearl type, the colour, the size in millimetres and the number of pearls. Those four details, read together with the seven factors, explain most of the distance between two jewels that at first glance look alike.

The seven factors, one by one: How a pearl is judged. The maison's four pearls: Akoya, Freshwater, South Sea, Tahiti. For a one-of-a-kind piece or an exceptional pearl, the maison offers a dedicated consultation.

Text by the MIMÍ Milano gemmologists · updated 9 September 2026