A crystal of bismuth. The oxide layer on the surface is iridescent, accounting for the wide array of colors. Courtesy Richard Bartz, via Wikipedia
Bismuth is a metallic chemical element (atomic number 83). It's compounds are used for a number of purposes, including cosmetics and pigments. In medicine, bismuth subsalicylate is commonly used for treatment of gastro-intestinal disorders including nausea, heartburn and diarrhea - it is the active ingredient in Pepto-Bismol(TM). Historically, bismuth compounds were also used to treat burns and STDs.
Bismuth has properties similar to lead, but is far less toxic (it is one of the least toxic metals). As such, it is replacing lead in many industrial applications.