Galaxite is the manganese (Mn) rich endmember of the aluminium (Al) series of the spinel group. Divalentiron (Fe) and magnesium (Mg) readily substitute for the manganese in the crystal structure. Trivalent iron may also substitute for the aluminium. Thus, reflecting most natural samples, the formula may be better represented as (Mn,Fe2+,Mg)(Al,Fe3+)2O4.[3]
Galaxite generally occurs as small granular aggregates with a red-brownish tone. It has a vitreous luster and leaves a brownish-red streak. It is rated 7.5 on the Mohs Scale.[3]