Does a ruby have any other uses besides jewelry?

Rubies have found application in several fields like laser applications (due to its chromium content), as bearings for Swiss-made watches, to treat sunstroke and nosebleeds in ancient medicine, and even as the red color in red glass and porcelain when added in significant quantities (though synthetic rubies are more efficient for this due to lower cost & ease of manufacture). However, it might be argued that their most widespread applications remain to be in personal, industrial, scientific & medical purposes.