On this historic piece there is a half-inch thick crust of sparkling dark green and brown crystals of plattnerite growing over a limonite matrix. Here and there it is dotted with thin, tabular, transparent, 4mm crystals of wulfenite, in a bright yellow color. This is a very fine specimen from Mina Ojuela, featuring small, black, terminated, highly lustrous crystals. Plattnerite is a relatively rare lead dioxide. Towers and knobby aggregates of sparkly acicular crystals cover the matrix. This is an undamaged, classic, old-time specimen from the 1960s, and it comes with an old tyed label identifying it as coming from the old Colorado State Historic Society (apparently they no longer have a mineral collection), and also that it is ex-Richard C. Groom & Bruce C. Dundon.