any of a group of hard glassy minerals of variable colour consisting of oxides of aluminium, magnesium, chromium, iron, zinc, or manganese and occurring in the form of octahedral crystals: used as gemstones
2.
a hard, glassy mineral composed of magnesium-aluminium oxide found in metamorphosed limestones and many basic and ultrabasic igneous rocks. Formula: MgAl2O4
Word origin
C16: from French spinelle, from Italian spinella, diminutive of spina a thorn, from Latin; so called from the shape of the crystals
spinel in American English
(spɪˈnɛl; ˈspɪnəl)
noun
a variously colored, crystalline mineral, MgAlO4, used as a gem; magnesium aluminum oxide
Word origin
Early ModE spynel < MFr spinelle < It spinella, dim. of spina, thorn, spine < L: see spine