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A jewel bearing is a hard, polished stone — historically ruby or sapphire, both forms of corundum — pierced or cupped to support a pivot, pallet stone or impulse jewel with far less friction and wear than a bare metal pivot running in a metal plate. The fastest-moving and most-loaded pivots benefit most, which is why jewelling starts at the escapement and balance and works outward as quality rises.
Early jewelling used natural stones, hand-selected, cut and drilled by specialist jewellers, which made a fully jewelled movement expensive and jewel count a genuine marker of grade. The standard sequence — 7 jewels for a basic lever movement, rising through 11, 15, 17 and 21 as train bearings and endstones are added — reflects which pivots were considered worth jewelling at each price point.
The turning point was the Verneuil flame-fusion process, developed in the 1890s and applied to watch jewels in the early twentieth century: synthetic corundum grown in a furnace, chemically identical to natural ruby but cheap, consistent and available in quantity. Synthetic stones were actually superior for the purpose — free of the flaws and colour-sorting problems of natural stones — and by the 1920s they had displaced natural jewels almost entirely.
Cheap jewelling changed what a jewel count meant. Once stones cost little, makers could add jewels for marketing rather than function, and the mid-century saw watches advertised with implausibly high counts, some including non-functional or purely decorative stones. The 17-jewel full-train lever remained the honest standard; beyond 21 or so, extra jewels need a mechanical explanation — automatic winding, a chronograph, a calendar — to be taken seriously.
Settings matter as much as stones. Jewels may be pressed directly into the plate, or set in metal chatons (bushings) screwed to the plate — the better, more repairable arrangement, and a traditional mark of high-grade work. A 'jewelled' claim on a dial is a specification statement, not a condition report: jewels chip, crack and work loose, and only examination shows what state they are in.
For the collector, the practical reading is: 7 jewels is a sound basic movement, 15–17 is a good one, 21 and above should be explained by complications or automatic work, and chaton settings indicate quality intent. A high count with no visible function is a warning sign about the maker's honesty, not a bonus.
The Verneuil process and synthetic corundum
The conceptual origins of horological jewel bearings date back to 1704, when Nicolas Fatio de Duillier and Peter and Jacob Debaufre obtained an English patent for using natural stones like garnet, ruby, and sapphire to reduce pivot friction. While early experiments in synthetic stone creation occurred throughout the 19th century, including the work of Gaudin and Edmond Frémy, these efforts initially produced small crystals or required complex chemical processes. The invention of the Verneuil flame-fusion process, publicly announced by Auguste Verneuil in 1902, provided the first commercially viable method for industrial-scale synthetic corundum production. This technique utilizes an oxyhydrogen flame to melt finely powdered alumina and chromium oxide, which then recrystallizes into a single crystal structure known as a boule.
The industrial expansion of this technology was rapid, with significant production facilities established in Switzerland and the United States. Following the founding of Hrand Djevahirdjian’s factory in Monthey in 1914, global output grew from thousands of kilograms in the early 20th century to hundreds of thousands of kilograms by the end of the century. Although the process remains largely unchanged today, it requires highly pure alumina, often processed through the Bayer method, to avoid opacity caused by impurities. Synthetic stones produced via flame fusion can often be identified under magnification by the presence of microscopic gas bubbles and characteristic curved growth lines, which contrast with the straight inclusions found in natural gemstones.
Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.