Pronunciation: (spi-nel', spin'l), [key]
1. any of a group of minerals composed principally of oxides of magnesium, aluminum, iron, manganese, chromium, etc., characterized by their hardness and octahedral crystals.
2. a mineral of this group, essentially magnesium aluminate, MgAl2O4, some varieties being used as gems. Also,spi•nelle'.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.