Vanadinite, Pb5(VO4)3Cl (Lead Chlorovanadate), is a secondary mineral formed by alteration of lead ore by water. The mineral is light sensitive and so specimens should be kept in darkness. The bright orange colouration gradually darkens and dulls to shades of brown.

Description: A thin brown crystalline matrix covered by a crust of Vanadinite crystals. There are many, averaging about 1 to 2mm and some are only clearly visible under magnification. Almost all are small botryoids standing upright from the matrix. The colour is green, with a bright luster, showing good reflections.

Location: Hull Mine, Yuma Co. Arizona, USA.