Cultured pearls: what it really means

Introduction

The expression “cultured pearls” often causes misunderstanding. In gemmology it denotes a precise process: the human hand starts the formation of the pearl, and the mollusc carries it to completion with its own biological means, over a span of years.

Understanding what it really means helps in judging a pearl jewel correctly, and in recognising the simplifications that circulate on the subject.

What follows rests on gemmological criteria shared internationally and on the experience gathered in selecting and working pearls in fine jewellery.

What a “cultured pearl” means

A cultured pearl comes about like this: the human hand places a small sphere of mother-of-pearl, the nucleus, inside the mollusc. The animal responds by coating it with exceedingly thin layers of calcium carbonate, held together by a web of conchiolin. It repeats the operation thousands of times, and the material that results is called nacre — in Italian perlagione, and also mother-of-pearl.

The human role consists in starting the process and in maintaining the conditions in which the pearl can grow well: water quality, temperature, daily care of the farms.

A cultured pearl is in every respect an authentic pearl. The material that coats it is the one produced by the mollusc, laid down layer upon layer over the years, and cultured pearls today account for almost all the pearls used in quality jewellery.

Cultured pearls and natural pearls

Natural pearls form by pure accident, when a foreign body enters the mollusc. They are exceedingly rare, and they remain destined above all for collecting. Cultured pearls, by contrast, are the foundation of the whole sector, and they assure quality, continuity and control.

Two gems that fine jewellery still uses today remain natural: the conch and the melo, produced by two gastropods and impossible to cultivate. They are either found, or they are missing.

The time factor

The quality of a cultured pearl depends in large part on the time spent in the water. The longer the mollusc works, the thicker and more compact the nacre it lays down.

Nacre thickness governs three things: the lustre, because it is the layer the light passes through; how the surface withstands daily wear; and the condition of the pearl thirty years from now. Thin nacre wears away with rubbing, and the nucleus begins to show through.

That thickness stays invisible to the eye: fresh from the water, a pearl with thin nacre and one with generous nacre have the same surface. What tells them apart is time.

Why cultivation is a standard of quality

Cultivation makes it possible to choose the environment, the species of mollusc and the growing conditions with precision. From this come constant quality control and a rigorous selection of the pearls destined for jewellery.

The final quality always arises from the balance between human intervention, natural conditions and time.