The structure is rhombohedral and consists of a stack of several puckered layers of bismuth atoms: the atoms are positioned above and below the mean plane of each layer. In its highly pure form, bismuth can develop iridescent crystals—exhibiting yellow, blue, pinkish-purple, and dark green hues—which are commonly sold as collector's items. Lead-free bismuth compounds are used in the cosmetics industry and in medical applications. Rainbow Bismuth Crystals Specimen 157 grams 1 Piece - 64 x 53 x 32 mm about please be careful with the description and measures COMBINED SHIPPING (if you buy more items in the same auction you only pay 1 shipment) Standard shipping ( 2-7 days for Italy ) ( 10-20 days for Europe ) ( 15-40 days for rest of the world )