What Are Jewels in a Watch? The History, Craft, and Science Behind Them

Jewels in a watch are tiny, precisely shaped stones — usually synthetic ruby — placed inside the movement to act as low-friction bearings for its moving parts. They aren’t decoration. They’re what allows a mechanical watch to run smoothly, accurately, and for decades, without its metal gears grinding themselves apart.

If you’ve ever peered through the caseback of a mechanical watch and spotted small reddish-pink dots scattered across the movement, that’s what you were looking at. Here’s the full story of the jewel — where it came from, how it’s made, and what it actually does.

A Brief History of the Watch Jewel

The idea is over 300 years old. In 1704, Swiss mathematician Nicolas Fatio de Duillier, along with Peter and Jacob Debaufre, patented the technique of using hard stones as bearings inside watch movements. Before this, watchmakers used metal-on-metal pivots, which wore down quickly and needed constant oiling and servicing.

Early jewels were cut from actual gemstones — diamond, sapphire, ruby, and even garnet were used, and many of these early stones were simply small offcuts left over from gem-cutting. The problem was cost and labour: shaping these bearings required diamond-abrasive tools and enormous manual skill, which kept jewelled movements rare and expensive.

That changed in the early 1900s. In 1902, French chemist Auguste Verneuil developed a process to grow synthetic ruby and sapphire artificially, which made jewelled bearings dramatically more affordable — and it’s why jewels became a standard part of watchmaking rather than a rare luxury.

How Watch Jewels Are Made

Modern watch jewels are grown, not mined. Manufacturers create synthetic corundum (the mineral family that includes ruby and sapphire) in a lab, then cut and shape it into tiny doughnut-shaped bearings. While the old method relied on grinding with diamond abrasive, today jewels are typically shaped using high-powered lasers, chemical etching, and ultrasonic milling — processes precise enough to work at a scale of microns.

There are a few different types found inside a movement:

• Hole jewels – small ring-shaped stones that a gear’s pivot spins inside
• Cap jewels – flat stones that sit above hole jewels to reduce vertical friction
• Roller/impulse jewels – found in the pallet fork, these transmit the “tick” of the escapement

How Jewels Actually Work Inside a Watch

A mechanical watch is a chain of tiny gears (the “going train”) transferring energy from the mainspring to the balance wheel, which ticks back and forth thousands of times an hour. Every one of those gears has a pivot — a thin metal axle — that needs somewhere to spin.

If that pivot spun directly against the brass plates of the movement, friction and wear would slow it down and eventually damage the watch. Ruby is one of the hardest natural materials after diamond, and it’s naturally smooth at a microscopic level, so it lets the metal pivot spin with almost no resistance and barely any wear — even after decades of use.

This is also why jewels don’t need oil to function the way metal bearings do, though a small amount of lubricant is still used to further reduce friction and keep the movement running consistently across different temperatures.

Understanding “Jewel Count” on a Watch

You’ll often see watches described as “17 jewels” or “21 jewels.” A fully jewelled time-only movement typically has around 15 jewels covering the balance wheel, escapement, and going train — the fastest-moving, highest-friction parts of the watch.

Jewel count became a well-known marker of quality over the 20th century because it reflected genuine engineering — the more precision points in a movement, the more care and craftsmanship typically went into building it. It’s a small detail, but it’s part of what makes horology such a fascinating craft: even the tiniest, least-visible components carry centuries of engineering behind them.

FAQs

Are watch jewels real gemstones? Not anymore. Modern watch jewels are almost always synthetic ruby or sapphire, grown in a lab rather than mined, which makes them more consistent and affordable than natural stones.

Why are watch jewels usually red? The red colour comes from trace amounts of chromium added during the synthetic ruby-growing process. It’s a byproduct of the manufacturing method, not a design choice.

Does every watch have jewels? Most mechanical watches do, since jewels reduce friction at points that experience constant motion. Quartz watches, which have far fewer moving mechanical parts, may use very few or none at all.