blue-green

The Periodic Spiral assigns the color blue-green to scandium, manganese, copper, arsenic, actinium and the actinons, bohrium, unununium, and ununpentium. Of these, scandium, manganese, and copper all have interesting physical associations with the blue-green hue. The presence of scandium causes the blue-green color in aquamarine, a form of beryl, and in the related gem material bazzite (Be3[Al,Sc]2SiO6). Manganese, the basis for the pigments Manganese Blue and Manganese Green, is a primary constituent of phosphophyllite, a rare, blue-green, zinc and manganese gem mineral (Zn2[Fe, Mn] [PO4]2 - 4H2O, Hydrated Zinc Iron Manganese Phosphate. Copper tarnishes to a characteristic, and in may cases desirable, blue-green color in the presence of atmospheric sulfur and chlorine. Among the many copper-rich minerals noted for their pleasing blue-green hues are turquoise, azurite (Cu3(CO3)2.Cu(OH)2), malachite (a copper carbonate, CuCO3.Cu(OH)2), chrysocolla (a hydrated copper silicate), and cornetite (copper phosphate hydroxide). A "blue-green" color in water is ordinarily a sign of copper contamination, whereas the blue-green color of treated timber is the result of copper naphthanate and copper-chrome-arsenate that have been introduced under pressure to help protect the wood from borers.