I recently purchased some titanium foil from GalliumSource. They sent magnesium. My first inkling of a problem was an extremely vigorous reaction between the foil and hydrochloric acid. It also formed small bubbles when placed in water and reacted violently with copper chloride. It was not shiny, showing a film of oxidation typical of magnesium. It was remarkably light but not remarkably strong, unlike titanium. After a short email discussion, I received word that I was receiving a replacement piece of titanium foil.
http://www.youtube.com/watch?v=3a0cSP5pSkc&feature=youtu.be shows several properties of this magnesium foil, demonstrating obvious differences from titanium.