This Gem Looks Like Amethyst, Has A Color Range Like Quartz, But Isn’t Often Used In Jewelry

A CLASSIC GEMOLOGY LESSON is to place me beside amethyst and see who — based on color alone — can tell us apart (it is but folly to try). While purple is my hallmark color, it is but just one in my wide spectrum. In terms of range of color, I am rivaled only by quartz. And whereas some varieties of quartz can dazzle, I glow. I am luminescent, sometimes even phosphorescent. I’m also pretty darn useful. I am used as a flux in the production of steel and aluminum, as an added mineral in water, to make camera lenses and telescopes. The one area I’m not so commonly employed is jewelry — too soft they say. Still there’s hardly a budding gemologist in the world who doesn’t own at least one specimen of me.

Who am I?