Rolex and many other fine timepiece manufacturers utilize precious stones such as sapphires or rubies in the key pivot points in the automatic movement.  This reduces friction and wear. 

The idea of using jewels in the movement was introduced over 300 years ago, but is commonplace today. 

Depending on the complications in the timepiece you may find anywhere from 17 to as much as 100 jewels utilized in any given caliber.  The Rolex Submariner calibre 3135 utilizes 31 jewels.  The Rolex Daytona is powered by a calibre 4130 and has 44 jewels. 



Some jewels might be cosmetic.  However, many of the jewels used today are synthetic jewels, so they are inexpensive to produce.  Rolex utilizes synthetic rubies as a "bearing" to keep the parts of the watch friction-free for the most part.  The Rolex Daytona movement pictured above has a complex chronograph complication and so it requires more jewelry in order to keep friction to a minimum.