Turn over almost any mechanical or automatic watch with a display caseback and you'll see them: small red or pink dots set into the movement. Many people assume they're decorative, or a sign of luxury. They're neither. Those rubies are working parts, and they're one of the main reasons your watch keeps accurate time.
A mechanical watch is a machine of spinning gears, axles, and levers. Each wheel turns on a tiny pivot, and in early watches those steel pivots turned directly inside brass or steel holes. Metal rubbing against metal creates friction, and friction causes two problems:
Before the early 1700s, this was simply accepted. Pocket watches of the era could drift by many minutes a day, and they wore out far faster than a modern watch.
In 1704, Swiss-born mathematician Nicolas Fatio de Duillier, working in London with French watchmakers Peter and Jacob Debaufre, patented a method of drilling holes through tiny gemstones and using them as bearings inside watch movements. Instead of steel turning in metal, the pivots now turned in an extremely hard, smooth jewel.
The result was less friction, less wear, and more consistent timekeeping. It was a simple idea with enormous consequences.
Rubies aren't used because they're expensive. They're used because they're incredibly hard. Ruby is a form of corundum and rates 9 on the Mohs hardness scale, second only to diamond. That hardness means:
For nearly two centuries, natural gemstones made jeweled movements costly, so only the finest watches had them. That changed in 1902, when French chemist Auguste Verneuil introduced a flame-fusion process for growing synthetic rubies in a laboratory. Lab-grown rubies are chemically the same as natural ones: just as hard, just as smooth, at a fraction of the cost.
That breakthrough is why virtually every mechanical watch today, from a $300 Seiko to a $100,000 Patek Philippe, uses synthetic ruby jewels.
A fully jeweled basic mechanical movement typically has 17 jewels, placed at the points of highest friction: the balance wheel, the escapement's pallet fork and impulse jewel, and the pivots of the gear train. Automatic movements often have 21 to 28 jewels to support the rotor and winding system. Complex watches with chronographs or perpetual calendars can have 40, 60, or even more than 200. Every one of them has a job. None are there for decoration.
Here's what fascinates collectors most: the principle Fatio de Duillier patented in 1704 is essentially the same one inside a Rolex Submariner, Patek Philippe Nautilus, Audemars Piguet Royal Oak, or Vacheron Constantin Overseas today. Materials have improved and manufacturing is far more precise, but the core idea, a steel pivot turning in a hard jewel bearing, hasn't changed in more than three centuries.
Very few technologies survive that long. Most inventions from the 1700s are museum pieces. The jeweled bearing is still on your wrist.
That longevity says something about the people who created it. The watchmakers and inventors of the 1700s had no computers, no simulation software, no AI, and no electron microscopes. They worked with hand tools, magnifying lenses, careful observation, and patient trial and error. Every solution had to be reasoned out, tested by hand, and refined over years.
They weren't necessarily smarter than people today, but they had to think harder. Without tools to do the thinking for them, they built deep understanding of how things work from first principles. Today, answers are a search or a prompt away, and that convenience is genuinely useful. But it also makes it easy to skip the hard thinking that leads to real understanding.
That may be the deepest reason collectors love mechanical watches. A mechanical movement is a small monument to human problem-solving: hundreds of parts, designed by people working only with their hands and minds, solving problems so well that their answers are still in use more than 300 years later.
Yes. Modern watch jewels are synthetic rubies, which are real corundum with the same chemical makeup and hardness as natural rubies. They simply have no gemstone resale value.
Not automatically. Jewels should be where they're needed. A well-made 17-jewel manual watch can be excellent, while extra jewels only add value when the movement's complexity requires them.
Some do, usually just a few in the gear train, but quartz watches rely on a battery and quartz crystal for accuracy, so jewels matter far less than in mechanical watches.
Nicolas Fatio de Duillier, together with Peter and Jacob Debaufre, patented jewel bearings for watches in London in 1704.
Next time you look through a display caseback, take a closer look at those little red dots. They're more than 320 years of human ingenuity, still working every second.
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