| Minium | |
|---|---|
Minium druse on cerussite from the Old Yuma Mine, Tucson Mountains, Arizona |
|
| General | |
| Category | Oxide mineral |
| Chemical formula | Pb2+2Pb4+O4 |
| Strunz classification | 04.BD.05 |
| Dana classification | 07.02.08.01 |
| Crystal symmetry | Tetragonal (4/m 2/m 2/m) ditetragonal dipyramidal |
| Unit cell | a = 8.811(5) Å, c = 6.563(3) Å; Z = 4 |
| Identification | |
| Color | Scarlet to brownish red, may have a yellowish tint |
| Crystal habit | Scaly; commonly as earthy, pulverulent masses |
| Crystal system | Tetragonal |
| 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 |
| Refractive index | n = 2.42 |
| References | [1][2][3] |
Minium is the naturally occurring form of lead tetroxide, Pb2+2Pb4+O4. It is a light to vivid red and may have brown to yellow tints. It typically occurs as scaly to earthy masses. It crystallizes in the tetragonal crystal system.[1]
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. It occurs associated with galena, cerussite, massicot, litharge, native lead, wulfenite and mimetite.[1]
It occurs in a variety of worldwide areas in relatively small amounts. It occurs at Langhecke, Hesse; Badenweiler, Baden-Wurttemberg; 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. In the USA it is reported from the Jay Gould mine, Alturas County, Idaho; the Leadville district, Lake County, Colorado; in the Tonopah-Belmont mine, Maricopa County, Arizona. It also occurs in Eschuchapa and Guerrero, Mexico.[1] Good specimens were produced by a mine fire at the Broken Hill mine in New South Wales, Australia.[4]
It was named for the Iberian river known to the ancient imperial Romans as Minius, now known as Miño in modern Spanish and Minho in modern Portuguese. The name was originally applied to certain forms of cinnabar coated with the oxide, but after the observable material was determined to be chemically distinct from the cinnabar crystals that it coated, the name minium was applied to the red lead contaminant.[2]