Formula: MgAl2O4
Origin of name: from Latin spinella meaning little thorn, after crystal shape
Crystal system: cubic
Crystal class: 4/m -3 2/m
Twinning: common by spinel law
Unit cell: a = 8.083 Å
Colour: red, blue, green, brown, black
Diaphaneity:
Luster: vitreous to nearly dull
Habit: crystals octahedral, may be modified, or cubic, or dodecahedral, massive, compact to coarse granular, rounded grains
Hardness: 7.5 to 8
Specific gravity: 3.58
Cleavage: 1; {111} parting, indistinct
Tenacity: conchoidal or uneven, brittle
Streak: white
Synonyms/varieties: celonite (Fe-rich variety), pleonaste (Fe-rich variety)
Comments: series with magnesiochromite, with gahnite and with hercynite
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