massicot(n = noun.substance) massicotite - the mineral form of lead monoxide; in the form of yellow powder it is used as a pigment;
is a kind of lead ore

   Lead monoxide (also called Lead protoxide), PbO, obtained as a yellow amorphous powder, the fused and crystalline form of which is called litharge; lead ocher. It is used as a pigment. It is also called lead oxide yellow, as opposed to red lead, which is lead tetroxide Pb3O4. [1913 Webster]
" Massicot is sometimes used by painters, and also as a drier in the composition of ointments and plasters." [1913 Webster]

massicot, n. yellow lead monoxide, used as a pigment.

Etymology:
F, perh. rel. to It. marzacotto unguent prob. f. Arab. mashakunya