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
a hard, glassy mineral composed of magnesium-aluminium oxide found in metamorphosed limestones and many basic and ultrabasic igneous rocks. Formula: MgAl2O4
C16: from French spinelle, from Italian spinella, diminutive of spina a thorn, from Latin; so called from the shape of the crystals
A hard, variously colored cubic mineral, having usually octahedral crystals and occurring in igneous and metamorphosed carbonate rocks. The red variety is valued as a gem and is sometimes confused with the ruby. Chemical formula: MgAl2O4.
Any of a group of minerals that are oxides of magnesium, iron, zinc, manganese, or aluminum.