The two different valences of lead occupy different locations in the spinel type structure. Minium's structure is not exactly the same as spinel as spinel is an isometric mineral and minium is a tetragonal mineral. The small size of the lead ions, no doubt, cause a distortion in the spinel structure. Color is red, scarlet to brick-red. Luster is greasy to adamantine.
Crystals are opaque.
Also massive and granular. Crystals are generally well striated. Cleavage is perfect in several directions. Fracture is uneven. Hardness is 2.5 - 3.