Galena or lead glance is lead sulfide (PbS) which crystallizes in a close-packed cubic structure as shown in the picture (yellow = S, black = Pb). Diadochy for both lead and sulfur is common. Therefore natural galena usually comprises other (half) metals (Ag, Sn, Zn, Cd, U, Sb, As) as well as chalkogenites (Se, Te). Galena may degrade through weathering or biocorrosion into lead sulfate and lead carbonate respectively. The dark grey to black specimen of this gallery originates from the Kateřina coal mine in Radvanice (Czech Republic). It shows distinct iridescence if lit with white LED light.