A gemstone is a mineral, rock (such in the case of lapis lazuli), or petrified material that when cut or faceted and polished is collectible or ...
en.wikipedia.org/wiki/Jewels

Jewels is a 1968 album by Waylon Jennings on RCA Victor.
en.wikipedia.org/wiki/Jewels (album)

Synthetic sapphires or rubies that act as bearings for gears in a mechanical watch. The jewels reduce friction to make the watch more accurate and longer lasting.
www.wristwatchhut.com/glossary/

Instead of using a metal ball bearing in the works of a watch, a semi precious jewel (usually a ruby) is used instead. This insures that the ball bearing can not rust.
reviews.ebay.com.au/Dictionary-of-Costume-Jewelry_W0QQugidZ10000000000703742

The 3: ti-ratana (qv).
urbandharma.org/udharma2/dictionary/bd13.html

Jewels are inserted in, mainly watches, to reduce friction on the gear train. Until the 20th century, watch jewels were made of ruby, sapphire, aquamarine, garnet, and diamond. I have seen colourless jewels which might be quartz, or low grade (colourless) aquamarine. ...
www.clockswatches.com/papers/glossary.htm