sorry about the bad link. I can't find the original now, but this site :
http://www.welding-advisers.com/Mate...ification.html
Says :
"One can readily distinguish between light alloys like aluminum and magnesium with a simple test, but you should use the help of a chemist. Aluminum is attacked by caustic soda (NaOH), which is a dangerous material, and also by alkaline solutions, while magnesium is not. Conversely magnesium is attacked rapidly by usual inorganic acids (excluding hydrofluoric and chromic acid), while aluminum is not attacked by acids like nitric and sulfuric. Also aluminum density is about twice that of magnesium. "
This site says that "Magnesium is white and will not polish":
http://www.englishcustompolishing.co...aluminum1.html