Aluminum

 Aluminium is remarkable for the metal's low density and for its ability to resistcorrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates. Despite its prevalence in the environment, aluminium salts are not known to be used by any form of life. In keeping with its pervasiveness, aluminium is well tolerated by plants and animals. [6] Owing to their prevalence, potential beneficial (or otherwise) biological roles of aluminium compounds are of continuing interest. Credit to Wikipedia for the info: http://en.wikipedia.org/wiki/Aluminium