Watch Jewels: What Do They Do and Why Do They Matter?

Those who are very new to appreciating watches may be surprised, and a bit confused, upon reading about a watch that boasts “21 jewels” and afterward looking it over and finding no diamonds or emeralds or any other precious stones on its dial or case. Many watches do, in fact, offer such adornments, but those are not what’s being referred to on a watch’s spec sheet in the “jewels” column; to clarify, “jewels” in horological parlance are not shorthand for “jewelry.”

A watch’s jewels are, in fact, not even really intended to be seen and admired. Like the screws and gears and tiny wheels inside a watch’s movement, they are there to do a job, to play a vital and functional role in the smooth operation of a watch’s timekeeping. 

So what are jewels in a watch movement, anyway, and what are they for? And do watchmakers really use valuable, precious gems as workhorse components inside these micromechanical engines? On the latter question, well, yes and no. As to the former question, read on. 

The movement in a mechanical watch is a machine with lots of moving metal parts that tend to rub and grind against one another, creating friction that can wear down these components, adversely affecting the performance of the watch and ultimately shortening its functional life. The challenge in the early days of watchmaking was finding a substance harder than these metal parts to place at the vital pivot points to reduce metal-on-metal wear and tear. The answer presented itself shortly after the dawn of the 18th century: precious stones like diamonds, sapphires and rubies (the latter two both derivatives of corundum) were not only more resilient on the Mohs hardness scale than the metal (usually brass) used in watch movements, but also less abrasive on their surfaces. 

Watchmaking brothers Peter and Jacob Debaufre and their partner Nicolas Fatio, all from Switzerland, were the first to equip their watch movements with jewel bearings — jewels with pivot holes drilled in their centers for metal spindles, set into holes drilled in the movement’s plates and bridges — and even received an English patent for the development. Other watchmakers followed suit. Initially, shards of natural rubies — which are harder than sapphires and less expensive than diamonds — were widely used, but watchmakers experimented with other gemstones like garnet and quartz as well. In 1902, the French chemist Auguste Verneuil (below) developed his “flame fusion” process of inexpensively synthesizing gemstones like corundum and its varieties, which ushered in the modern process of using synthetic rubies instead. (This development also eventually led to the use of synthetic sapphire for watch crystals, as I detail here.)

Jewels in a watch movement come in several types, each with their own shape, properties, and intended role. Hole jewels, mounted on a wheel’s axle or pivot, are shaped like tiny doughnuts, with flat bottoms, rounded tops, and holes drilled in their center. Cap jewels, aka “capstones,” have no holes drilled in them and are used to minimize the motions of a balance staff; used in conjunction with springs on either end, they aid in shock resistance. Pallet jewels are rectangular-shaped and found at the ends of both arms of a pallet fork, the component in the movement’s lever escapement that regulates the flow of energy between the balance wheel and escape wheel. A roller jewel (or impulse jewel) is situated inside the pallet fork and serves as the connection point between the escape wheel and pallets. 

A watch’s movement is said to be “fully jeweled” when it carries at least 17 of these synthetic rubies. In a standard time-only mechanical watch, they are distributed thusly: two cap jewels, two pivot jewels, and one roller jewel in the balance wheel; two pivot jewels and two pallet jewels in the pallet fork; and two pivot jewels each for the escape wheel and the third, fourth, and center wheels. As one might expect if one has gotten this far, a more complicated watch’s movement will have more moving parts and thus, more jewels. In fact, the 17 cited above are standard in manually wound mechanical calibers; a 21-jewel movement, with additional stones added for positional errors, is considered the baseline for many aficionados these days, and an automatic movement should have at least 25. (Quartz movements, which have far fewer mechanical moving parts, may have few jewels or none, and they keep time just fine without them.)

Which begs the question one so often hears from newbies: do more jewels in a watch necessarily make it more valuable? In a word, no. The jewels themselves are worth virtually nothing: remember, they’re all synthetic these days, and have been for a long time. This did not stop some watch companies, in the early to mid-20th century, from adding non-functional jewels to their watches simply so they could play up the perceived value of jewels in their marketing: Waltham once sold a watch that boasted 100 jewels in its movement, the vast majority of them entirely ornamental. This somewhat unscrupulous practice persisted until 1974, with the establishment of the ISO 1112 standard that prohibited watch companies from including unnecessary (i.e. non-functional) jewels in their advertising.

A higher jewel count in a watch, while not an instant signifier of its prestige or value, does speak to its mechanical complexity and very likely its timekeeping performance. Under the modern ISO rules, more jewels in a mechanical watch equal less friction and, possibly, additional complications beyond simple timekeeping. The number of jewels is also determined in part by how many movement parts are required to achieve all the watch’s functions.  A. Lange & Söhne’s 1815 Flyback Chronograph has 40 jewels to support the intricate stopwatch mechanism in its 306-part Caliber L951.5, for example, while Vacheron Constantin’s Overseas Perpetual Calendar makes do with 36 jewels in its 276-part movement, Caliber 1120. The intricately embellished movement of Breguet’s horological chef d’oeuvre from 2020, the Classique Double Tourbillon 5345 Quai de l’Horloge (below), consists of no less than 738 parts, and an astonishing 81 jewels to ensure the smooth operation of its dual independently rotating tourbillon escapements. While watch jewels are not the type of gemstones you’d give to celebrate an anniversary, to many a watch enthusiast they are worth their weight in gold.