Lead(II,IV) oxide, also called red lead or minium, is the inorganic compound with the formula Pb3O4. A bright red or orange solid, it is used as pigment, in the manufacture of batteries, and rustproof primer paints. It is an example of a mixed valence compound, being composed of both Pb(II) and Pb(IV) in the ratio of two to one.
Lead(II,IV) oxide
Minium from a mine fire at Broken Hill, Australia
Minium, also known as red lead or red lead oxide, is a bright orange red pigment that was widely used in the Middle Ages for the decoration of manuscripts and for painting. Often mistaken for less poisonous cinnabar and vermillion, minium was one of the earliest pigments artificially prepared and is still in use today. It was made by roasting white lead pigment in the air; the white lead would gradually turn yellow, then into an orange lead tetroxide. Minium's color varied depending upon how long the mineral was roasted.
The Códice del Escorial (1272–1284) from Spain. Medieval manuscripts often used red-orange minium pigment in the letters of the text and for small illustrations, called miniatures.
A sample of minium pigment, made by roasting white lead pigment
Solid minium