What is Massicot?
Massicot is a small but vivid clue to ore alteration. Its yellow powdery coatings contrast with dark galena and red lead oxides, creating a compact study in polymorphism and oxidation.
Mineralogy and crystal structure
Reference formula: PbO. Massicot is the orthorhombic polymorph of lead oxide, dimorphous with litharge. It is usually earthy or fine-grained and may occur with bright red lead oxides and secondary lead carbonates. Massicot is classified with oxides and has a orthorhombic crystal system. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 9.3–9.7.
Colour, lustre and habit
Typical colours include yellow, yellow-orange, red-brown. The usual powdery, granular, massive habit and earthy, resinous, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Massicot forms in or is associated with oxidation of galena and other lead ores in mine workings and surface alteration zones. Important documented localities include the United States, Germany, France, Mexico, Australia and the United Kingdom.
Yellow lead oxide from the weathering zone
Massicot is a small but vivid clue to ore alteration. Its yellow powdery coatings contrast with dark galena and red lead oxides, creating a compact study in polymorphism and oxidation.
Collecting and care
Lead-bearing and soft: keep enclosed, avoid dust, acids and cutting, and wash hands after handling.
