If you have ever looked closely at a mechanical watch and seen “21 jewels” written on the dial or case back, you might have wondered what that actually means. Are there really gemstones inside the watch? And if so, what purpose do they serve?

The answer is yes, in a way. But not in the way you might expect.

What Are Jewels in a Watch?

In watchmaking, jewels are not decorative gemstones. Instead, they are tiny pieces of synthetic ruby or sapphire that are built into the movement of a mechanical watch. Their purpose is to reduce friction and wear in the areas where moving parts constantly interact. This helps keep the watch running accurately and reliably over time.

Why Use Jewels at All?

Mechanical watches have many moving components such as gears, wheels, and pinions. These parts can rub against each other thousands of times every hour. Without something to minimize friction, those components would wear out quickly. Jewels are incredibly hard materials, second only to diamonds on the Mohs hardness scale. This makes them ideal for reducing friction and resisting wear.

Where Are These Jewels Used?

You will usually find these jewels placed at key points inside the watch movement. These include:

• The pivot points of gears
• The balance wheel and escapement
• The pallet fork
• The winding mechanism
• The calendar or date system

If your watch has a transparent case back, you may be able to see some of these tiny red or pink stones within the movement.

A Quick History of Watch Jewels

The use of jewels in watches began in the early 1700s. Swiss innovators such as Nicolas Fatio de Duillier and the Debaufre brothers were among the first to use natural rubies and diamonds in timepieces. At that time, jewels were a luxury feature found only in high-end watches. During the 20th century, watchmakers began using synthetic rubies and sapphires instead. This development made jewel-bearing technology more affordable and accessible.

What Does “17 Jewels” or “21 Jewels” Actually Mean?

The number of jewels in a watch refers to how many jewel bearings are used in the movement. A basic mechanical watch typically contains 17 jewels, which is usually enough to support all the critical friction points. Watches that include additional features, such as automatic winding systems or calendar functions, may have 21 or more jewels to accommodate the extra moving parts.

However, having more jewels does not always mean a better watch. After a certain point, additional jewels do not improve performance and may simply be added for marketing purposes. The quality of the movement and overall craftsmanship are more important than the jewel count alone.

How Many Jewels Does a “Good” Watch Have?

Most high-quality mechanical watches contain between 17 and 25 jewels. Some vintage models may have as few as 7 or 11 jewels. More complex modern watches, such as chronographs or perpetual calendars, may use 30 or more jewels due to the added complications.

Conclusion: Jewels In A Watch

• Why they are used: Jewels reduce friction and extend the lifespan of the movement.
• What they are made of: Most jewels are synthetic rubies or sapphires.
• Where they are located: Jewels are found at pivot points, gear trains, escapements, winding mechanisms, and calendar components.
• How many is typical: A good mechanical watch usually contains between 17 and 25 jewels.
• Are they decorative? No. These jewels serve a functional purpose and are different from decorative gems found on watch cases or dials.

Understanding the role of jewels in a watch gives you a deeper appreciation for the craftsmanship behind mechanical timepieces. Whether you are considering a simple hand-wound Seiko or a complex Swiss chronograph, you now know what those jewel numbers mean and why they matter.