What Are Jewels in a Watch? Why 17, 21 or 24 Jewels Matter

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Jewels in a watch are tiny bearings, almost always made of synthetic ruby or sapphire, that the steel pivots of a mechanical movement turn in. They cut friction and wear at the points that move most, which helps the watch keep better time and last longer between services. A "17 jewels" or "24 jewels" marking tells you how many of these bearings the movement uses, not that it contains gemstones of any value.

If you own an automatic, its jewels are working every second. Here is what they are, where they go, and what the number on the dial really means.

What watch jewels are made of

Watch jewels are corundum, the same mineral as natural rubies and sapphires. Early jewels were natural stones such as diamond, sapphire, ruby and garnet. That changed in 1902, when Auguste Verneuil invented a process for making synthetic sapphire and ruby, which made jewel bearings far cheaper. Today, nearly all watch jewels are synthetic.

Why corundum? It is extremely hard (sapphire rates 9 on the Mohs scale) and very smooth when polished, so a steel pivot can spin in it for years with little wear. The red color you see in most movements comes from the synthetic ruby; it is a convention, not a sign of quality.

Why a watch needs jewels

A mechanical movement is a chain of gears, called the train, that releases the mainspring's energy in tiny, regular steps. Each gear turns on thin steel pivots. Where those pivots run in plain metal holes, friction is high and the holes wear oval over time, which upsets the watch's rate.

Jewels fix that. The friction figures make the point: the static coefficient of friction for brass on steel is about 0.35, against 0.10 to 0.15 for sapphire on steel. Less friction means:

• More consistent timekeeping, because energy reaches the balance wheel more evenly.
• Less wear, because the hard jewel does not wear oval the way brass does.
• Longer service life, as long as the movement is cleaned and oiled on schedule.

Jewel bearings are not new. They were invented for watches in 1704 by Nicolas Fatio de Duillier, Peter Debaufre and Jacob Debaufre, who received an English patent for them.

Where the 17 jewels go

Seventeen jewels is the classic count for a "fully jeweled" time-only watch, with hours, minutes and seconds and nothing else. They sit at the points of highest speed and load:

The balance wheel and escapement get the most jewels because they move fastest and decide how accurately the watch runs. The slower parts near the mainspring, such as the barrel, often run without jewels in basic movements.

Why automatic watches have more jewels

An automatic adds a whole winding system: a rotor that spins on its own bearing and a set of reversing or reduction wheels that turn its motion into mainspring tension. A date or day-date adds more moving parts. Many of those parts benefit from jewel bearings too, so automatic movements typically list more than 17.

Some real examples from makers' published specs:

Seiko does not publish where each jewel sits, but the pattern is clear: the more functions a movement has, the higher the count. Our guide to how automatic watches work shows the winding system those extra jewels support.

What about 21, 23 or 25 jewels?

Counts like these usually mean a 17-jewel base plus jewels for automatic winding, a calendar or a more complex train. There is no universal map, though, and makers differ in which parts they jewel. Treat the number as a rough guide to how complex the movement is, not a quality score.

Does a higher jewel count mean a better watch?

Not on its own. A well-made 17-jewel manual watch can be finer than a 25-jewel automatic, because quality depends on the design, the finishing and how well the movement is regulated. Jewels only help where they serve as bearings. Extra jewels in places that do not need them add a bigger number to the dial and nothing to the watch.

Use the jewel count as a sanity check instead:

• Fewer than 17 in a mechanical watch suggests some important bearings are unjeweled, which is common in very cheap movements.
• 17 or more in a manual watch means the essential bearings are covered.
• About 21 to 29 in an automatic is normal for a mainstream movement with automatic winding and a date.

Accuracy specs, power reserve and service history tell you more. For what to expect on accuracy, see our guide on how accurate automatic watches are.

Can you see the jewels?

Yes, on many watches. A display caseback shows the jewels as small red dots set into the bridges and plates, often surrounded by gold-colored chatons on finer movements. An open-heart dial lets you watch the balance wheel, whose jewels and impulse pin do the most work, from the front. Skeleton watches show even more; our skeleton watch guide covers them.

Jewels in quartz and pocket watches

Quartz watches rarely use jewels in any meaningful number. Their hands need so little torque that the bearings carry almost no load, so jewels add little. Vintage pocket watches, by contrast, often advertised their jewel counts proudly, because before synthetic stones were cheap, jeweling was expensive and a real mark of quality.

Do jewels need maintenance?

The jewels themselves do not wear out in normal use, but the oil on them ages. Most jewel bearings in a watch are lubricated, and old, thick oil raises friction and wear. That is why mechanical watches need periodic service: Seiko's customer service FAQ asks owners to bring a watch in every three years for examination, cleaning and oiling. Our guide on how often to service an automatic watch covers other brands.

Shock protection systems, which let the balance jewels move slightly and spring back, protect the balance pivots from breaking when a watch is knocked. Most modern mechanical movements have one.

Common misconceptions

• "The jewels make the watch valuable." They are synthetic and worth very little on their own.
• "More jewels always means better." Only jewels that serve as bearings help.
• "Jewels never need service." The jewels last; the oil on them does not.
• "Quartz watches have lots of jewels." Most have few or none, because there is almost no load to bear.

FAQ