Watch Jewels Explained: Why Your Movement Has Rubies In It
What Are Jewels in a Watch Movement?
Open a watch spec sheet and you will see "21 jewels", "24 jewels", sometimes "31 jewels". No — these are not gemstones decorating the dial. Watch jewels are tiny synthetic ruby or sapphire bearings placed at the movement's friction points.
Why Movements Need Jewels
Metal gears spinning against metal plates wear out, create friction, and drain energy. Synthetic rubies solve this:
- Extreme hardness: corundum rates 9 on the Mohs scale — gears pivot in near-wear-free cups
- Low friction: less energy lost means longer power reserve
- Oil retention: jewel sinks hold lubricant exactly where pivots need it
What the Numbers Mean
| Jewel Count | Where They Sit | Typical Use |
|---|---|---|
| 17–21 | Escapement and train wheel pivots — everything that actually runs | Standard functional count; NH35-family movements use 24 |
| 24–27 | Adds automatic winding system bearings | Modern automatics |
| 30+ | Covers every conceivable pivot plus extras | Prestige movements; diminishing returns beyond ~27 |
The key insight: beyond roughly 21–24 jewels, extra counts add little functional value. Marketing loves big numbers; watchmakers do not.
Are Jewels Real Gemstones?
They are real corundum — the same mineral as sapphire and ruby — but grown in laboratories for purity and consistency. A movement's jewels cost cents to produce; their value is engineering, not rarity.
Practical Takeaways for Buyers
- A 21-jewel automatic is fully jeweled where it matters
- Higher counts signal more complete winding-system bearing coverage — nice, not essential
- If a seller advertises "jewels" as a luxury feature driving price up, be skeptical
Our entire NH35-based range uses properly jeweled modern automatics — see any model in the Sub Diver collection for spec examples.
Frequently Asked Questions
Do jewels ever need replacing?
Almost never — they outlast several service intervals. Shock can crack one rarely; servicing addresses it.
Is a 17-jewel watch bad?
Not inherently — hand-wound classics ran fine on 17. Check that the automatic rotor section is also borne if the watch self-winds.
Can you see the jewels?
Through an exhibition caseback, yes — they appear as small red dots at pivot points.