Gemmology and gem-setting are the two disciplines that allow Rolex watches to be endowed with diamonds, sapphires and other precious stones. Strict quality control of the gemstones, via a range of specialist methods, ensures that gem-set models sparkle with exceptional intensity.
With a swift and steady movement, the gem-setter picks up a trapeze-cut diamond the size of a pinhead with a pair of tweezers. They place it delicately into a groove in the bezel of a future Oyster Perpetual Cosmograph Daytona in platinum. The stone sits slightly too high. The gem-setter carefully scoops a minute speck of metal from the cavity with a graver; the gap reduces, but does not disappear. They will repeat this process again, three times on average, until the table of the stone – its topmost facet – is perfectly aligned with its neighbour. The dimensions of the gemstones vary in tiny proportions, and Rolex tolerates variances of no more than 2 hundredths of a millimetre, which is around a quarter of the diameter of a human hair. Gem-setters therefore employ all their skill and experience to work the metal, and to place the stone in the optimal position. Once finished, 36 diamonds will form the perfectly uniform, radiant circle of the watch’s gem-set bezel. This bezel alone illustrates the wide range of skills and know-how mastered in-house by Rolex. The process begins by sourcing the most striking stones, and then deciding how best to showcase them, as the art of gem-setting lies in ensuring that the sparkle and beauty of each stone is fully revealed.
Rolex uses only the highest quality gemstones. Whether it be diamonds or precious stones, such as rubies, sapphires or emeralds, they must always be the best. This includes the cut of the stone in particular – for which exact dimensions are required – as well as the clarity, colour and the number of carats. Rolex’s know-how comes into play from the initial quality control of the stones, to refining the range of colours, and to the gem-setting process itself.
The rigorous testing protocol that is applied when gemstones are received relies as much on human expertise as on state-of-the-art equipment. During qualitative analysis, diamonds and coloured gemstones are subject to the same criteria. The way in which the gemstones are cut – the symmetry and shape of the facets – determines the way in which light penetrates the stones and is reflected off the underside, the area known as the pavilion. The cut therefore directly influences the stones’ luminosity. In the case of diamonds, a well-cut stone accentuates the intensity and number of reflections, which can even result in rainbow hues. Clarity relates to the absence of faults in a stone. As the gemstones are natural, it is not unusual for inclusions to be present.
However, Rolex keeps only the most translucent stones. For diamonds, no inclusions must be present when the stone is observed at 10 x magnification. The final criterion, colour, is always evaluated by eye, requiring the gem-setter’s seasoned aesthetic judgement. To complete the process, the stones are compared against certified master stones. Rolex uses only the most colourless diamonds; they must be within the highest grades of the Gemological Institute of America colour chart – in colour ranges D to G. Thanks to tests carried out with specialist tools, including some that are specially designed by the brand, all stones used in Rolex watches are perfectly uniform, and of the very highest quality.
The precious stones are then entrusted to the gem-setters. With movements as precise as watchmakers, they set each stone, one by one, into the watches. Their craft is multifaceted.
They begin by deciding upon the layout and colours of the stones in collaboration with designers. They then work with the engineers in charge of the external elements of the watch, i.e. all components that are not linked to the movement. Together they study the future placement of the stones to prepare, to the nearest micron, the gold or platinum into which the stones will be set. Their task is to determine, for each stone, the amount of metal required to hold it in place.
Patiently, the gem-setter then sets the stone in the optimal position, gently pushing the surrounding metal into place around the stone to hold it securely. The skill of the gem-setter is showcased in their ability to choose the appropriate tool, to find the right angle, and to apply just the right amount of force. A final polish makes the tiny metal setting shine, and highlights the stone’s intense sparkle. This step is repeated up to almost 3,000 times on certain diamond-paved dials.