What is Jewels?

In the intricate world of watchmaking, jewels play a crucial role in the performance and longevity of a mechanical movement. They are not decorative elements but precision-engineered components designed to reduce friction between moving parts, thereby ensuring the smooth and efficient functioning of the mechanism. Typically made from synthetic rubies, these tiny bearings help maintain accuracy, minimise wear, and extend the lifespan of a watch.

Jewels are among the most essential yet least visible components of a mechanical watch. Their presence reflects centuries of technological refinement and a deep understanding of physics and material science. Without them, the fine interplay of gears, levers, and escapements that define horology would quickly succumb to wear and inaccuracy.

The Origins of Jewels in Watchmaking

The use of jewels in timekeeping mechanisms dates back to the early 18th century. The invention is attributed to Nicolas Fatio de Duillier and Pierre and Jacob Debaufre, who patented the use of jewels as bearings in watch movements in 1704. Their goal was to create a material hard enough to resist the friction and wear that plagued metal components.

Before this innovation, early watchmakers relied on metal bushings and pivots, which wore down quickly due to constant motion and lack of effective lubrication. The introduction of jewels represented a revolution in horological engineering, significantly improving durability and precision.

Initially, natural gemstones such as sapphire, ruby, and garnet were used because of their hardness and ability to maintain a polished surface. These stones were painstakingly cut and drilled by hand, making jeweled movements extremely expensive and reserved for the finest timepieces.

By the early 20th century, the development of synthetic rubies made jewel bearings more accessible and consistent in quality. These synthetic stones possessed the same physical properties as natural rubies but could be produced in large quantities at a fraction of the cost. This advancement helped establish jewelling as a standard practice in watchmaking.

The Function of Jewels

Jewels in a watch serve as low-friction pivot points for the rotating components of the movement. They are typically placed at points where metal parts, such as gear pivots or escapement components, come into contact. The hardness of ruby, combined with its ability to retain a smooth surface, minimises friction and wear.

In a typical watch movement, jewels perform three primary functions:

1. Reducing Friction
   Jewels act as bearings that allow metal parts to rotate smoothly. Without them, friction between steel components would generate heat, wear, and debris, eventually affecting accuracy.

2. Maintaining Accuracy
   Reduced friction ensures more consistent movement of gears and the escapement. This consistency directly contributes to better timekeeping precision over long periods.

3. Increasing Longevity
   Because rubies are nearly impervious to wear, they prevent damage to delicate pivots and prolong the lifespan of the movement.

Each jewel is carefully shaped, polished, and set into the mainplate or bridge of the movement. The pivots of the moving parts rest inside tiny concave holes within the jewels, which are lubricated with a thin layer of oil to further reduce friction.

Types of Jewels in a Movement

The jewels in a mechanical movement can be divided into several types based on their function and location.

1. Hole Jewels
   These are the most common type and serve as bearings for rotating arbors and pivots. They contain a small hole drilled through the centre to accommodate the shaft of the gear or wheel.

2. Cap Jewels
   Flat jewels placed over hole jewels to reduce end-shake (axial play) in critical components such as the balance wheel or escapement. Cap jewels also retain lubrication and protect against dust and moisture.

3. Pallet Jewels
   Found in the escapement, these jewels are attached to the pallet fork and interact with the escape wheel. Their polished surfaces ensure smooth impulse transmission and precise energy release.

4. Impulse and Roller Jewels
   The impulse jewel, usually mounted on the balance roller, transmits energy from the pallet fork to the balance wheel. It is a key element in the escapement’s rhythm and timing.

5. Endstones
   Similar to cap jewels, endstones are used in high-grade watches to provide extra stability and shock protection for important parts such as the balance staff pivots.

Each of these jewel types plays a specific role in ensuring the efficiency and durability of the movement.

The Number of Jewels and What It Means

The number of jewels in a watch often attracts attention from collectors and enthusiasts. Many mechanical watches proudly display “17 jewels” or “25 jewels” on the dial or movement. While the count provides some information about the complexity of the mechanism, it does not necessarily indicate quality.

A standard manual-wind mechanical movement typically contains 15 to 17 jewels. These are positioned in the most critical friction points: the balance staff, escape wheel, pallet fork, and gear train. The addition of an automatic winding system, calendar functions, or other complications increases the jewel count, sometimes reaching 25, 30, or more.

Beyond a certain point, however, adding jewels becomes purely decorative or marketing-driven. Some manufacturers in the mid-20th century advertised exaggerated jewel counts to attract buyers, using synthetic jewels in non-functional positions. True watchmaking craftsmanship focuses not on quantity but on correct placement and function.

Materials and Manufacturing

Modern jewels are almost exclusively made from synthetic ruby, a crystalline form of aluminium oxide (Al2O3) with traces of chromium that give it a red hue. The material is created through a process known as the Verneuil method, which melts and crystallises aluminium oxide powder using an oxyhydrogen flame. The resulting crystal is extremely hard, measuring 9 on the Mohs scale—second only to diamond.

Once produced, synthetic rubies are cut, drilled, and polished to microscopic tolerances. Each jewel must be perfectly smooth to avoid damaging the pivots it supports. The entire process demands precision machinery and skilled craftsmanship, as even the smallest imperfection can affect performance.

Occasionally, sapphire (a colourless variant of the same material) or other synthetic gemstones are used instead of ruby, but their physical properties are virtually identical. The choice often depends on aesthetic preference or cost considerations.

The Role of Lubrication

Although jewels significantly reduce friction, they do not eliminate the need for lubrication. A thin layer of special watch oil is applied to each jewel bearing to further minimise resistance and protect the pivots from wear.

Over time, these oils can degrade or evaporate, leading to increased friction and decreased accuracy. Regular maintenance, including cleaning and re-lubrication, is essential to preserve the performance of a jeweled movement. In high-end watches, the placement and amount of lubricant are controlled with extraordinary precision to achieve optimal efficiency.

Jewels and Watchmaking Evolution

The introduction of synthetic jewels marked a turning point in the evolution of horology. Before their widespread adoption, jewel setting was a luxury available only to expensive watches. With industrial production, even mid-range watches gained the benefit of jeweled bearings, improving accuracy and reducing servicing needs.

The innovation also spurred advancements in other areas of watchmaking. As movements became more reliable, manufacturers could pursue thinner, more complicated, and more precise designs. Jewels made it possible to build calibres capable of operating for decades without major wear.

In modern mechanical watches, jewels are also part of the aesthetic narrative. Watchmakers often leave them visible through transparent casebacks, their crimson or pink tones standing out against the metallic plates and bridges. Beyond their technical function, they symbolise the marriage of science and beauty that defines fine watchmaking.

Jewels in Quartz and Modern Movements

Even quartz watches, which rely on electronic oscillators instead of mechanical escapements, may include jewels in their gear trains. Although fewer are required, these jewels serve the same purpose of reducing friction and prolonging movement life.

In hybrid or high-frequency mechanical watches, where components move at extremely high speeds, jewel placement becomes even more critical. Some advanced materials, such as silicon, are now used alongside jewels to further enhance efficiency and reduce the need for lubrication. Yet despite technological progress, synthetic ruby bearings remain irreplaceable in traditional mechanical engineering.

The Symbolism of Jewels in Horology

Beyond their technical function, jewels represent a broader philosophy within horology. They are a reminder that precision is achieved not only through complexity but through refinement of detail. Each jewel, perfectly polished and precisely placed, embodies the watchmaker’s pursuit of perfection.

Collectors often view the jewel count as part of a watch’s personality, a reflection of its mechanical soul. A glance at the glimmering red bearings through the caseback reveals not ornamentation, but the hidden craftsmanship that allows time itself to flow smoothly.

Conclusion

Jewels are the unseen guardians of mechanical precision. Their presence ensures that the energy of the mainspring flows efficiently through the gear train, escapement, and balance wheel, allowing a watch to perform accurately over decades of use.

From their invention in the 18th century to the precision-engineered components of today, jewels have become an indispensable part of watchmaking history. They represent both scientific innovation and artistic mastery, uniting beauty and utility in the heart of every fine mechanical movement.

In the quiet rhythm of a ticking watch, every jewel plays its part—a silent partnership between material and motion that keeps time alive.