spinelle

/spɪˈnɛl/
noun
  1. A hard, glassy mineral that comes in various colors (especially red, blue, or black) and is sometimes used as a gemstone.
    • Mineral collectors value spinelle for its brilliant colors and hardness.
    • The museum displayed a beautiful red spinelle from Sri Lanka.
    • She wore a ring with a large blue spinelle that sparkled in the light.