Minium (mineral)

Minium, also red lead, chemical lead (II, IV ) oxide, is a rarely occurring mineral from the mineral class of oxides and hydroxides. It crystallizes in the tetragonal crystal system with the chemical composition Pb22 Pb4 O4 and usually forms powder or masses and only microscopic crystals of bright red or brownish- red color.

Etymology and history

Minium was described in 1806 by James Smithson for the first time systematically. He reported in a letter to Joseph Banks from Kassel about the exact locality not stated. The mineral was known to the Romans in ancient times, which gave it its name. In the Middle Ages the name was bowdlerized to redlead.

Classification

In the classification by Strunz Minium is counted among the oxides with a ratio of metal to oxygen of 3:4. After the 8th edition forms a group together with Apuanit, Kusachiit, Schafarzikit and Versiliait. The 9th edition, it forms a separate sub-group of the oxides, with a ratio of metal to oxygen of 3:4, and only large cations.

In the classification by Dana Minium forms a separate subgroup of multiple oxides with the general formula ( A B2 ) 2X4 ( spinel group).

Education and Locations

Minium forms as a rare secondary mineral in lead deposits by aging. Frequently likely are responsible fire in the mines for education. It is associated with galena, cerussite, Massikot, litharge, lead, Wulfenite and Mimetit.

There is a larger number of localities known ( 222 of 2010), but are usually only found small amounts Minium in the individual deposits. These include long hedge, Badenweiler, Bleialf, Horhausen and other localities in Germany, Mežica in Slovenia, Leadhills in Scotland, Saint- Avold in France, Långban in Sweden, Sarrabus - Gerrei in Sardinia (Italy ), Anarak in Iran, Tsumeb in Namibia, Alturas County, Leadville and Maricopa County in the United States and Eschuchapa in Mexico.

Crystal structure

Minium crystallizes in the tetragonal crystal system in space group P42/mbc with the lattice parameters a = 8.811 Å and b = 6.653 Å and four formula units per unit cell. Note that minium oxide is not, but a lead ( II) orthoplumbat.

Use

Due to its intense color Minium was since ancient times as a red pigment used (see also → Lead (II, IV ) oxide ). Because of its toxicity, it is however no longer used today.