So you're about to buy a mechanical watch. One with a crystal back and/or front.
But after a while you’re wondering what those little purple ‘gems’ are between the steel elements of the mechanical movement. Those purple ‘gems’ are called jewels that, today, are made of synthetic rubies. But all of the jewels used in the nineteenth century and early years of the twentieth century were made from natural gem stones, in the main rubies and sapphires.
Jewels were developed for movements of mechanical watches to reduce friction at the points of heaviest wear. When metal rubs again metal and when oil breaks down, the damage to pivots and bearings can be rapid and devastating in terms of watch repairs. In order to reduce friction between two pieces of metal that rub against each other, watch makers use hard stones as friction points as they last a lot longer than metal. Jewelling does reduce the wear, and thereby prolongs the life of a watch, but it also increases cost. The more jewels a watch has, the more pieces its movement has. And the more jewels a watch has, the higher the price.