Pb₂₁Cu₂₀Cl₄₂(OH)₄₀.6H₂O

This sample of cumengite is displayed in the Smithsonian Museum of Natural History. Cumengite is a chloride of copper and lead with the composition Pb₂₁Cu₂₀Cl₄₂(OH)₄₀.6H₂O. The large sample at left is about 12 cm across. This mineral been also labeled cumengeite.