spinel
Concise Oxford English Dictionary © 2008 Oxford University Press:
spinel /spɪˈnɛl, ˈspɪn(ə)l/
▶noun a hard glassy mineral consisting chiefly of magnesium and aluminium oxides.
■ Chemistry any of a class of similar crystalline oxides.
– origin C16: from Fr. spinelle, from Ital. spinella, dimin. of spina ‘thorn’.
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