Definition of "spinel"

spinel

/spɪˈnɛl/

noun
countable and uncountable, plural spinels
1. (mineralogy) Any of several hard minerals of cubic symmetry that are mixed oxides of magnesium and aluminium and are used as gemstones of various colours.
  Quotations
  Although there are dozens of different types of gems, among the best known and most important are […] . (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)
  2012 March, Lee A. Groat, “Gemstones”, in American Scientist‎, volume 100, number 2, archived from the original on 14 June 2012, page 128
2. (solid state chemistry) Any crystalline material, not necessarily an oxide, that possesses the same crystal structure as this mineral.
3. Bleached yarn in making the linen tape called inkle; unwrought inkle.