What exactly is a gemologist? And why does Rolex need one?

You might have spotted the Rolex Oyster Perpetual Submariner Date in our latest Watches, Jewellery and Luxury Annual Edition. It’s been the ultimate dive watch since the 1950s but this year’s model is a design knockout in 18kt white gold with a unidirectional rotatable bezel set with nine light-blue and 27 dark-blue baguette-cut sapphires, 11 baguette-cut diamonds and one triangular diamond at 12 o’clock. Not to mention that the case lugs and crown guard are set with 92 brilliant-cut diamonds and the design comes together around a blue dial with a sunray finish.

To adorn its timepieces with the most striking gemstones, Rolex has in-house gemologists and gem-setters. The gemologists are responsible for examining gemstones, retaining only those that meet Rolex’s stringent quality criteria. The stones then pass into the hands of the gem-setters, who are tasked with placing and fixing each stone to best reveal its beauty, colour and sparkle.

Rolex has offered gem-set watches throughout its history. In embellishing its timepieces with precious stones, the brand endows them with an alternative aesthetic, while conserving their identity and technical features, such as reliability, robustness and resistance to magnetic fields and shocks.

Upon their arrival at the ateliers, all gemstones - both diamonds and coloured stones – undergo rigorous verification procedures. To guarantee the quality of the stones, gemologists have a range of analysis tools, in addition to their expertise. These tools, some of which are specially developed for Rolex, can provide information on the stones’ chemical composition. Diamonds, for example, are tested via X-ray imaging to confirm their authenticity.

The colour of the diamond is evaluated by the naked eye and calls for seasoned judgment. In their assessment, expert gemologists compare the diamonds against certified master stones. The brand chooses to use only the most colourless diamonds, which must fall within categories D to G – the highest grades on the Gemological Institute of America colour scale. This meticulous analysis ensures all the gemstones on a watch are uniform and of the best quality.

Once approved by the gemologists, the precious stones are entrusted to the gem-setters. With the precision of a watchmaker, they set each stone, one by one, onto the watches.

A gem-setter’s craft is multifaceted. First, decisions are made with designers about the colour and arrangement of the stones. This is an exercise in finding a balance between aesthetic and technical requirements. Then follows a consultation with the case and bracelet engineers. Together they study the future placement of the stones in order to prepare, to the nearest micron, the gold or platinum into which the stones will be set. For each stone, they determine the precise amount of metal required to hold it in place.