Two yellow-coloured lead oxide minerals
PbO
These two minerals differ only in their crystal structure, which is orthorhombic in the case of massicot, but tetragonal for litharge. They may both have been used by illuminators, but their identification by non-invasive methods is not straightforward. When detected, massicot usually appears in areas containing minium/red lead, either as an impurity in a natural sample or due to imperfect synthesis of a manufactured product.
