On this piece there is a crust of sparkling black crystals of plattnerite growing over a limonite matrix. This is a very fine specimen from Mina Ojuela, featuring small, black, acicular, distinctly terminated, highly lustrous crystals. Plattnerite is a relatively rare lead dioxide. Towers and knobby aggregates of sparkly acicular crystals cover one side of the matrix. This is an undamaged, classic, old-time specimen from the 1950s and 1960s finds.