Spī-nĕlle'

(spī-nĕl'), spinella, Sp. espinel, espinela, Ger. spinell, L. Lat. spinellus, from Lat. spina, a thorn, a prickle, probably so called from its pointed crystals.] (Min.) A mineral occurring in octohedrons, of great hardness, consisting of a sesquioxide and a protoxide in equal proportions, the former being usually alumina, but often partly sesquioxide of iron, the latter usually magnesia, but sometimes protoxide of iron, of zinc, &c. When of a red or ruby color, it constitutes the gem spinel-ruby, or the common ruby of jewelry. It occurs also of green, blue, brown, and black colors. Dana.