Early in the days of watchmaking, the internal gears and workings of watches were made of finely crafted metal. However, over time, as these parts work and wear against each other, even the strongest metal can wear away, impairing timekeeping and shortening the life of the watch.

To reduce the internal friction that creates wear over time, watchmakers began using jewels. Diamonds, the hardest jewels with a Mohs hardness scale rating of 10, are ideal for enduring wear and precision, but they are also extremely expensive and hard to work with. To reduce costs, many watchmakers instead used sapphires or rubies, with a hardness scale of 9: almost as hard as diamonds, but much more affordable, and workable with diamond-tipped tools and implements.

In those times, using jewels in the mechanism didn’t simply add to the expense of the raw materials used in making the watch. Jewels also need to be milled, sawed, and polished, with diamond-tipped tools, to tolerances as precise as just 5 microns. To make things more complicated, natural jewels also have small imperfections which might be acceptable in other applications, but that render them unsuitable for watches.

Because of the expense of the materials, the difficulty in crafting and repairing them, and the dramatic improvement jewels give to the longevity of a watch, the presence of jewels naturally became an important feature, and watchmakers would be sure to advertise the increased value by telling people how many jewels were in the watch. Even today, we see watches being advertised by the number of jewels they contain.

However, the number of jewels in a watch is far less important today than it was a century ago.

Today, the jewels used in watches are almost always synthetic rubies. These rubies still require precision crafting, but they are inexpensive to create and to use. Synthetic rubies also do not have natural imperfections and weaknesses, making them easier to work with and more reliable in watchmaking.

Synthetic rubies, like the natural jewels that came before them, are used to reduce friction and wear, and are used at almost all pivot points in the gear train. The number of jewels in a watch depends on the design of the movement, and the number naturally varies. However, because of the perceived value and marketing benefits of including jewels in a watch, many watches also include jewels where they aren’t strictly necessary to improve function, but simply to make the watch seem more valuable and prestigious.

In other words, jewels are essential for the longevity and reliability of a watch over time. However, today’s watch jewels are synthetically produced, and inexpensive, so they don’t add significantly to the cost of materials used in a watch. Most of the time when a watch is advertised as containing a lot of jewels, it’s simply meant to imply more quality in materials and craftsmanship, and doesn’t really impact the manufacturing cost.

In other words, if a watch is well-made and meant to last, it will naturally contain jewels for reduced friction and increased durability. But more jewels doesn’t necessarily mean it’s a better watch, or worth paying a higher price for.