Minium: Properties and Occurrences

Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4 also known as red lead. It is red lead oxide, sometimes found as a mineral but usually prepared synthetically; tri-lead tetroxide. It is a reddish oxide of lead, used as a pigment in paints and in glass and ceramics

Minium is rare and occurs in lead-mineral deposits that have been subjected to severe oxidizing conditions. It also occurs as a result of mine fires.

General Information

  • Category: Oxide mineral
  • Formula: (repeating unit) Pb2+2Pb4+O4
  • Crystal system: Tetragonal
  • Crystal class: Ditetragonal dipyramidal (4/mmm)
  • Color: Scarlet to brownish red, may have a yellowish tint.

Fig: Minium – a light-to-vivid red

Properties

Minium is a light-to-vivid red and may have brown-to-yellow tints. It typically occurs in scaly-to-earthy masses. It crystallizes in the tetragonal crystal system.

  • Crystal habit: Scaly; commonly as earthy, pulverulent masses
  • Cleavage: Perfect on {110} and {010}
  • Mohs scale hardness: 2.5
  • Luster: Dull to slightly greasy
  • Streak: Yellow-orange
  • Diaphaneity: Semitransparent
  • Specific gravity: 8.9 – 9.2
  • Optical properties: Uniaxial

Occurrence – A rare secondary mineral in some highly oxidized lead-bearing mineral deposits; may form during mine fires.

It occurs in relatively small amounts throughout the world: Langhecke, Hesse; Badenweiler, Baden-Württemberg; Bleialf, Eifel district; Horhausen; Rhineland-Palatinate in Germany. It occurs at Mies, Slovenia; Leadhills, Lanarkshire, Scotland; Castelberg St. Avold, Moselle, France; from Langban, Varmland, Sweden; Sarrabus, Sardinia, Italy; near Anarak, Iran; and Tsumeb, Namibia.

It also occurs in Eschuchapa and Guerrero, Mexico. Good specimens were produced by a mine fire at the Broken Hill mine in New South Wales, Australia.

Association: Galena, cerussite, massicot, litharge, lead, wulfenite, mimetite.